Absence Of CD4 Research Articles

Comparing methods for immobilizing HIV-1 SOSIPs in ELISAs that evaluate antibody binding

Enzyme-linked immunosorbent assays (ELISAs) are used to evaluate binding of broadly neutralizing antibodies (bNAbs) and polyclonal sera to native-like HIV-1 Env SOSIPs. Methods for immobilizing SOSIPs on plates differ, which can lead to variable or, in some cases, misleading results. Three methods used to immobilize SOSIPs were compared to determine how antigen immobilization methods affect Env conformation and ELISA results. HIV-1 SOSIPs were directly coated on polystyrene plates, captured by a monoclonal antibody against a C-terminal affinity tag, or randomly biotinylated and coated on a streptavidin plate. Binding of bNAbs with known epitopes were compared for each immobilization method. Binding of bNAbs targeting the V1V2, V3, CD4 binding site, and gp120/gp41 interface was comparable for all antigen immobilization methods. However, directly coated HIV-1 SOSIP ELISAs showed detectable binding of 17b, a CD4-induced antibody that binds a V3 epitope that is concealed on closed prefusion Env trimers in the absence of added CD4, whereas antibody-immobilized and randomly biotinylated Env-coated ELISAs did not show detectable binding of 17b in the absence of CD4. We conclude direct coating of HIV-1 SOSIPs on ELISA plates can result in exposure of CD4-induced antibody epitopes, suggesting disruption of Env structure and exposure of epitopes that are hidden in the closed, prefusion trimer.

Helios Expression Is Downregulated on CD8+ Treg in Two Mouse Models of Lupus During Disease Progression.

T-cell–mediated autoimmunity reflects an imbalance in this compartment that is not restored by tolerogenic immune cells, e.g., regulatory T cells or tolerogenic dendritic cells (tolDCs). Although studies into T-cell equilibrium have mainly focused on regulatory CD4+FoxP3+ T cells (CD4+ Tregs), recent findings on the lesser known CD8+ Tregs (CD44+CD122+Ly49+) have highlighted their non-redundant role in regulating lupus-like disease and their regulatory phenotype facilitated by the transcription factor Helios in mice and humans. However, there are still remaining questions about Helios regulation and dynamics in different autoimmune contexts. Here, we show the absence of CD8+ Tregs in two lupus-prone murine models: MRL/MPJ and MRL/lpr, in comparison with a non-prone mouse strain like C57BL/6. We observed that all MRL animals showed a dramatically reduced population of CD8+ Tregs and a greater Helios downregulation on diseased mice. Helios induction was detected preferentially on CD8+ T cells from OT-I mice co-cultured with tolDCs from C57BL/6 but not in MRL animals. Furthermore, the Helios profile was also altered in other relevant T-cell populations implicated in lupus, such as CD4+ Tregs, conventional CD4+, and double-negative T cells. Together, these findings could make Helios a versatile maker across the T-cell repertoire that is capable of differentiating lupus disease states.

Abstract 240: MERTK inhibition induces an anti-leukemia dendritic cell - T cell axis while TYRO3 inhibition protects through a separate mechanism

Abstract The TAM family receptor tyrosine kinases TYRO3, AXL and MERTK are potential therapeutic targets in a variety of cancers. In previous studies, inhibition of MERTK decreased PD-1 checkpoint proteins in the leukemia microenvironment and prolonged survival in a syngeneic BCR-ABL+/Arf-/- B-cell acute leukemia model, implicating MERTK as a promising immune-oncology target in leukemia. Strikingly, Mertk-/- mice were largely protected from leukemia. In our current studies, Tyro3-/- almost completely prevented development of leukemia, comparable to Mertk-/-, while Axl-/- mice died with similar timing to wild type (WT) mice (20-40 days). These data demonstrate differential roles for TAM kinases in the anti-leukemia immune response. Depletion studies were conducted to evaluate potential roles for T cells and dendritic cells (DCs) in anti-leukemia immunity in Mertk-/- mice. Selective depletion of CD8+ T cells abrogated protection from leukemia in Mertk-/- mice, but survival was still prolonged relative to WT. Thus, while CD8+ T cells were required for complete protection from leukemia, the anti-leukemia response remained partially intact even in the absence of CD8+ T cells, implicating an innate immune mechanism. Indeed, combined depletion of CD8+ T cell and CD8α+ DC subsets completely abrogated the anti-leukemic effects in Mertk-/- mice, revealing a critical immunosuppressive role for MERTK in DCs in the leukemia microenvironment. In contrast to Mertk-/- mice, selective depletion of CD8+ T cells completely abrogated protection from leukemia in Tyro3-/- mice, indicating a mechanism less dependent on DCs. Similarly, single cell RNA sequencing revealed CD8+ DCs with a more mature and antigen-presenting phenotype in Mertk-/- mice compared to WT, while antigen-presenting DCs were not increased in Tyro3-/- mice. Single cell sequencing data also suggest induction of an anti-leukemic DC - T cell axis in WT leukemic mice treated with the MERTK-selective inhibitor MRX-2843. DCs were nearly absent in leukemic bone marrow from saline-treated mice and were dramatically increased in response to treatment with MRX-2843. Treatment with MRX-2843 also decreased the incidence of CD8+ T cells expressing high levels of Tox, which has been associated with T cell exhaustion. These changes coincided with decreased leukemic blasts, even in the context of established disease.Together, our findings support a model whereby MERTK inhibition promotes DC function and CD8+ T cell activity, leading to anti-leukemia immunity. In contrast, anti-leukemia immunity in response to TYRO3 inhibition is less dependent on DCs. Differential roles for the TAM kinases in the leukemia microenvironment provide rationale for development of MERTK and/or TYRO3 targeted immunotherapies to treat acute leukemia. Citation Format: Justus M. Huelse, Swati S. Bhasin, Beena E. Thomas, Madison L. Chimenti, Xiaodong Wang, Stephen V. Frye, H. Shelton Earp, Manoj Bhasin, Deborah DeRyckere, Douglas K. Graham. MERTK inhibition induces an anti-leukemia dendritic cell - T cell axis while TYRO3 inhibition protects through a separate mechanism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 240.

CD4+ T helper 2 cells suppress breast cancer by inducing terminal differentiation.

Cancer immunology research is largely focused on the role of cytotoxic immune responses against advanced cancers. Herein, we demonstrate that CD4+ T helper (Th2) cells directly block spontaneous breast carcinogenesis by inducing the terminal differentiation of the cancer cells. Th2 cell immunity, stimulated by thymic stromal lymphopoietin, caused the epigenetic reprogramming of the tumor cells, activating mammary gland differentiation and suppressing epithelial-mesenchymal transition. Th2 polarization was required for this tumor antigen-specific immunity, which persisted in the absence of CD8+ T and B cells. Th2 cells directly blocked breast carcinogenesis by secreting IL-3, IL-5, and GM-CSF, which signaled to their common receptor expressed on breast tumor cells. Importantly, Th2 cell immunity permanently reverted high-grade breast tumors into low-grade, fibrocystic-like structures. Our findings reveal a critical role for CD4+ Th2 cells in immunity against breast cancer, which is mediated by terminal differentiation as a distinct effector mechanism for cancer immunoprevention and therapy.

Absence of CD4+ and CD8+ T cell expansion after primary multimodal treatment predicts early progression in inoperable stage III NSCLC.

e20590 Background: There are no blood-based biomarkers for survival prediction in inoperable stage III NSCLC patients. We propose a method for calculation of novel area under curve (AUC) biomarkers of the dynamic change of multiple leukocyte subpopulations before, during, and after thoracic irradiation (TRT), chemoradiotherapy (CRT), and chemo-radio-immunotherapy (CRT-ICI) in this patient cohort. The extracted biomarkers identify patients with early progression after TRT. Methods: 20 patients (17 male, 3 female), at median age of 65.5 years (range 34 to 79) were enrolled in the study. The median follow-up time was 60 weeks. Eleven patients suffered from adenocarcinoma, 8 squamous cell carcinoma, and 1 undifferentiated NSCLC. They received TRT (2/20, 10%), CRT (11/20, 55%), or CRT-ICI (7/20, 35%). One patient (1/20, 5%) withdrew consent and was excluded from analysis. Primary endpoints were progression free survival (PFS) at 6 and 12 months. Patient blood was analyzed via flow cytometry for 7 circulating leukocyte populations at baseline, twice during radiotherapy, at the end of radiotherapy (RTend), and 10, 20, 35, 48, and 60 weeks after enrollment. We analyzed CD3+ total T cells, CD4+ T cells, CD8+ T cells, CD19+/CD20+ B cells, CD3-CD56+ NK cells, CD56 bright NK cells, and CD56 dim NK cells. Here, we report on CD4+ and CD8+ T cells. The AUC from RTend to zenith of absolute cell counts provided aggregate measures for the time-course data. We performed hierarchical clustering and cluster characterization. Relevant features were selected by stepwise drop-out. Results: Clustering of the AUC between RTend and zenith for CD4+ T cells and CD8+ T cells delineated two prognostic groups. The favorable group was characterized by higher AUC values for CD4+ and CD8+ T cells compared to the unfavorable group. All patients (9/9, 100%) in the favorable group versus 36.4% (4/11) patients in the unfavorable group were progression-free at 6 months (Fisher´s exact test, two-tailed: p-value = 0.00472). This effect was observed as a trend with PFS at 12 months. Here 66.6% (6/9) of patients had PFS at 12 months in the favorable group versus 27.3% (3/11) in the unfavorable group (Fisher´s exact test, two-tailed: p-value = 0.175). There is a directly proportional relationship of the reported AUC values to PFS at 6 months and 12 months. Conclusions: Patients who responded with T cell expansion after immunogenic cell death by TRT, CRT, or CRT-ICI had significantly longer PFS compared to those without increase. Longitudinal monitoring of CD4+ and CD8+ T cells and the AUC from RTend to zenith is a promising biomarker for detecting early progression in the present study which is the subject of validation in an ongoing prospective study (PRECISION, NCT05027165).

Cyclic Adenosine Monophosphate (cAMP)-Dependent Phosphodiesterase Inhibition Promotes Bone Anabolism Through CD8+ T Cell Wnt-10b Production in Mice.

ABSTRACTCyclic adenosine monophosphate (cAMP)‐dependent phosphodiesterase (PDE) inhibitors such as pentoxifylline (PTX) suppress cAMP degradation and promote cAMP‐dependent signal transduction. PDE inhibitors increase bone formation and bone mass in preclinical models and are used clinically to treat psoriatic arthritis by targeting inflammatory mediators including activated T cells. T cell activation requires two signals: antigen‐dependent CD3‐activation, which stimulates cAMP production; and CD28 co‐stimulation, which downregulates cAMP‐signaling, through PDE activation. PDE‐inhibitors consequently suppress T cell activation by disrupting CD28 co‐stimulation. Interestingly, we have reported that when CD8+ T cells are activated in the absence of CD28 co‐stimulation, they secrete Wnt‐10b, a bone anabolic Wnt ligand that promotes bone formation. In the present study, we investigated whether the bone anabolic activity of the PDE‐inhibitor PTX, has an immunocentric basis, involving Wnt‐10b production by CD8+ T cells. When wild‐type (WT) mice were administered PTX, biochemical markers of both bone resorption and formation were significantly increased, with net bone gain in the axial skeleton, as quantified by micro‐computed tomography (μCT). By contrast, PTX increased only bone resorption in T cell knockout (KO) mice, causing net bone loss. Reconstituting T cell–deficient mice with WT, but not Wnt‐10b knockout (KO) CD8+ T cells, rescued bone formation and prevented bone loss. To study the role of cAMP signaling in Wnt‐10b expression, reverse‐transcription polymerase chain reaction (RT‐PCR) and luciferase‐reporter assays were performed using primary T cells. PDE inhibitors intensified Wnt‐10b promoter activity and messenger RNA (mRNA) accumulation in CD3 and CD28 activated CD8+ T cells. In contrast, inhibiting the cAMP pathway mediators protein kinase A (PKA) and cAMP response element‐binding protein (CREB), suppressed Wnt‐10b expression by T cells activated in the absence of CD28 co‐stimulation. In conclusion, the data demonstrate a key role for Wnt‐10b production by CD8+ T cells in the bone anabolic response to PDE‐inhibitors and reveal competing T cell–independent pro‐resorptive properties of PTX, which dominate under T cell–deficient conditions. Selective targeting of CD8+ T cells by PDE inhibitors may be a beneficial approach for promoting bone regeneration in osteoporotic conditions. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Three Models of Vaccination Strategies Against Cryptococcosis in Immunocompromised Hosts Using Heat-Killed Cryptococcus neoformans Δsgl1.

Vaccines are one of the greatest medical accomplishments to date, yet no fungal vaccines are currently available in humans mainly because opportunistic mycoses generally occur during immunodeficiencies necessary for vaccine protection. In previous studies, a live, attenuated Cryptococcus neoformans Δsgl1 mutant accumulating sterylglucosides was found to be avirulent and protected mice from a subsequent lethal infection even in absence of CD4+ T cells, a condition most associated with cryptococcosis (e.g., HIV). Here, we tested three strategies of vaccination against cryptococcosis. First, in our preventative model, protection was achieved even after a 3-fold increase of the vaccination window. Second, because live C. neoformans Δsgl1-vaccinated mice challenged more than once with WT strain had a significant decrease in lung fungal burden, we tested C. neoformans Δsgl1 as an immunotherapeutic. We found that therapeutic administrations of HK C. neoformans Δsgl1 post WT challenge significantly improves the lung fungal burden. Similarly, therapeutic administration of HK C. neoformans Δsgl1 post WT challenge resulted in 100% or 70% survival depending on the time of vaccine administration, suggesting that HK Δsgl1 is a robust immunotherapeutic option. Third, we investigated a novel model of vaccination in preventing reactivation from lung granuloma using C. neoformans Δgcs1. Remarkably, we show that administration of HK Δsgl1 prevents mice from reactivating Δgcs1 upon inducing immunosuppression with corticosteroids or by depleting CD4+ T cells. Our results suggest that HK Δsgl1 represents a clinically relevant, efficacious vaccine that confers robust host protection in three models of vaccination against cryptococcosis even during CD4-deficiency.

Helpless CD8 T cell memory explained: prolonged antigen presentation drives a temporal rather than terminal defect

Abstract CD4 T cell help is critical for long-term antiviral CD8 T cell immunity. Despite seemingly normal effector properties, “helpless” CD8 memory T cells (TM) generated in the absence of CD4 T cells during initial priming exhibit a substantially blunted recall response. Yet, how lack of CD4 help specifically impairs CD8 TM formation in the context of acute viral infections remains elusive. Here, we demonstrate that in transiently and constitutively CD4 T cell-deficient mice “helpless” antiviral CD8 TM to acute lymphocytic choriomeningitis virus (LCMV) exhibit a wide array of homeostatic, phenotypic, and functional defects that are broadly consistent with delayed CD8 TM maturation. Mechanistically, “helpless” CD8 T cell memory is not grounded in altered CD8 effector T (TE) cell differentiation in the absence of CD4 T cells but in exposure of post-effector CD8 T cells to protracted viral antigen presentation. Conversely, efficient generation of “helped” CD8 T cell memory is contingent on CD40L-mediated activities by LCMV-specific CD4 T cells that promote timely clearance of viral antigen. Importantly, we show that “helpless” memory-precursor CD8 TE display comparable memory potential to their “helped” counterparts, and that, once viral antigen is cleared, complete resolution of “helpless” CD8 memory is achieved over a period of ~1.5 years during which “helpless” CD8 TM eventually acquire mature TM properties including fully restored recall capacities. Collectively, our data redefine “helpless” CD8 T cell memory as a temporal rather than terminal defect, with implications for our general conceptualization of CD8 T cell memory as well as for the development of preventive and therapeutic strategies to improve protective CD8 TM function. Supported by grant NIH R01AI093637.

Response to anti-PD-1 and anti-LAG-3 immune checkpoint blockade is associated with induction of pro-inflammatory Tregs

Abstract Only a subset of patients durable clinical responses to aPD-1 and/or aCTLA-4 immunotherapies, thus, developing new therapeutic agents to increase the proportion of responding patients is a priority. Combining aPD-1 with aLAG-3 has shown promising results; however, lack of mechanistic understanding of aPD-1/aLAG-3 synergy remains a barrier for its optimal clinical use. Here, we examined the mechanism of aPD-1/aLAG-3 synergy in multiple mouse models using flow cytometry and single cell RNA sequencing. Combined aPD-1/aLAG-3 immunotherapy significantly improved the survival of CT26 (BALB/c; colon carcinoma) and MCA-205 (C57BL/6; sarcoma) tumor-bearing mice compared to monotherapy. Regulatory T cells (Tregs) suppressed response to this therapy, as in the absence of CD4+ T cells, 100% of mice responded. To understand how responders overcome Treg suppression, we performed an in-depth analysis of tumor-infiltrating lymphocytes (TIL) comparing mice that responded to treatment (decreased tumor size post-treatment) to non-responders (same tumor growth trajectory as control). Responders had reduced Foxp3+ CD4+ Tregs in comparison to non-responders and, in addition, those Tregs had a ‘fragile’ phenotype, including a pro-inflammatory cytokine profile (TNF-a; IFN-g), increased LAG-3, and decreased NRP1 expression. Within responders, CD8+ TIL exhibited increased frequency, effector cytokine production (TNF-a; IFN-g), and LAG-3 expression as compared to non-responders. Together, these data suggest that aPD-1/aLAG-3 can reduce Treg frequency and function leading to expansion of active tumor-specific CD8+ T cells capable of supporting tumor regression and improved survival. Supported by the Providence Portland Medical Foundation and GlaxoSmithKline

Antigen Cross-Presentation by Murine Proximal Tubular Epithelial Cells Induces Cytotoxic and Inflammatory CD8+ T Cells.

Immune-mediated glomerular diseases are characterized by infiltration of T cells, which accumulate in the periglomerular space and tubulointerstitium in close contact to proximal and distal tubuli. Recent studies described proximal tubular epithelial cells (PTECs) as renal non-professional antigen-presenting cells that stimulate CD4+ T-cell activation. Whether PTECs have the potential to induce activation of CD8+ T cells is less clear. In this study, we aimed to investigate the capacity of PTECs for antigen cross-presentation thereby modulating CD8+ T-cell responses. We showed that PTECs expressed proteins associated with cross-presentation, internalized soluble antigen via mannose receptor-mediated endocytosis, and generated antigenic peptides by proteasomal degradation. PTECs induced an antigen-dependent CD8+ T-cell activation in the presence of soluble antigen in vitro. PTEC-activated CD8+ T cells expressed granzyme B, and exerted a cytotoxic function by killing target cells. In murine lupus nephritis, CD8+ T cells localized in close contact to proximal tubuli. We determined enhanced apoptosis in tubular cells and particularly PTECs up-regulated expression of cleaved caspase-3. Interestingly, induction of apoptosis in the inflamed kidney was reduced in the absence of CD8+ T cells. Thus, PTECs have the capacity for antigen cross-presentation thereby inducing cytotoxic CD8+ T cells in vitro, which may contribute to the pathology of immune-mediated glomerulonephritis.

Crosstalk between CD4 T cells and synovial fibroblasts from human arthritic joints promotes hyaluronan-dependent leukocyte adhesion and inflammatory cytokine expression in vitro

The content and organization of hyaluronan (HA) in the extracellular matrix (ECM) have been identified as strong indicators of inflammation in joint disease, although the source and role of HA as an effector of inflammation is not clear. In this study, we established co-cultures of activated human CD4 T cells with fibroblast-like synoviocytes (FLS) from osteoarthritis (OA) and rheumatoid arthritis (RA) subjects and examined the role of HA in promoting inflammatory events. Co-cultures of RA FLS with activated CD4 T cells generated an HA-enriched ECM that promoted enhanced monocyte adhesion compared to co-cultures of OA FLS with activated CD4 T cells. In addition, both OA FLS and RA FLS co-cultures with activated CD4 T cells elicited significant increases in the expression of IL1β, TNF, and IL6, with the increase in IL6 expression most prominent in RA co-cultures. Blocking HA synthesis and accumulation with 4-methylumbelliferone reduced expression of IL6, IL1β, and TNF in both OA FLS and RA FLS co-cultures. The increase in HA synthesis in the co-cultures was mimicked by IL6 trans-signaling of FLS in the absence of CD4 T cells. Inhibition of HA synthesis blocked the increase in IL6 by RA FLS mediated by IL6 trans-signaling, suggesting that the HA synthetic pathway may be a key mediator in IL6 expression by FLS. Overall, our study indicates that HA-enriched ECM generated by co-cultures of activated CD4 T cells with FLS from human joints creates a pathogenic microenvironment by promoting adhesion of leukocytes and expression of inflammatory cytokines including IL6.

Tissue-resident memory CD8+ T cells cooperate with CD4+ T cells to drive compartmentalized immunopathology in the CNS.

In chronic inflammatory diseases of the central nervous system (CNS), immune cells persisting behind the blood-brain barrier are supposed to promulgate local tissue destruction. The drivers of such compartmentalized inflammation remain unclear, but tissue-resident memory T cells (TRM) represent a potentially important cellular player in this process. Here, we investigated whether resting CD8+ TRM persisting after cleared infection with attenuated lymphocytic choriomeningitis virus (LCMV) can initiate immune responses directed against cognate self-antigen in the CNS. We demonstrated that time-delayed conditional expression of the LCMV glycoprotein as neo-self-antigen by glia cells reactivated CD8+ TRM. Subsequently, CD8+ TRM expanded and initiated CNS inflammation and immunopathology in an organ-autonomous manner independently of circulating CD8+ T cells. However, in the absence of CD4+ T cells, TCF-1+ CD8+ TRM failed to expand and differentiate into terminal effectors. Similarly, in human demyelinating CNS autoimmune lesions, we found CD8+ T cells expressing TCF-1 that predominantly exhibited a TRM-like phenotype. Together, our study provides evidence for CD8+ TRM-driven CNS immunopathology and sheds light on why inflammatory processes may evade current immunomodulatory treatments in chronic autoimmune CNS conditions.

Induction of thymic atrophy and loss of thymic output by type-I interferons during chronic viral infection

Type-I interferon (IFN-I) signals exert a critical role in disease progression during viral infections. However, the immunomodulatory mechanisms by which IFN-I dictates disease outcomes remain to be fully defined. Here we report that IFN-I signals mediate thymic atrophy in viral infections, with more severe and prolonged loss of thymic output and unique kinetics and subtypes of IFN-α/β expression in chronic infection compared to acute infection. Loss of thymic output was linked to inhibition of early stages of thymopoiesis (DN1-DN2 transition, and DN3 proliferation) and pronounced apoptosis during the late DP stage. Notably, infection-associated thymic defects were largely abrogated upon ablation of IFNαβR and partially mitigated in the absence of CD8 T cells, thus implicating direct as well as indirect effects of IFN-I on thymocytes. These findings provide mechanistic underpinnings for immunotherapeutic strategies targeting IFN-1 signals to manipulate disease outcomes during chronic infections and cancers.

Invariant NKT Cells Promote the Development of Highly Cytotoxic Multipotent CXCR3+CCR4+CD8+ T Cells That Mediate Rapid Hepatocyte Allograft Rejection.

Hepatocyte transplant represents a treatment for metabolic disorders but is limited by immunogenicity. Our prior work identified the critical role of CD8+ T cells, with or without CD4+ T cell help, in mediating hepatocyte rejection. In this study, we evaluated the influence of invariant NKT (iNKT) cells, uniquely abundant in the liver, upon CD8-mediated immune responses in the presence and absence of CD4+ T cells. To investigate this, C57BL/6 (wild-type) and iNKT-deficient Jα18 knockout mice (cohorts CD4 depleted) were transplanted with allogeneic hepatocytes. Recipients were evaluated for alloprimed CD8+ T cell subset composition, allocytotoxicity, and hepatocyte rejection. We found that CD8-mediated allocytotoxicity was significantly decreased in iNKT-deficient recipients and was restored by adoptive transfer of iNKT cells. In the absence of both iNKT cells and CD4+ T cells, CD8-mediated allocytotoxicity and hepatocyte rejection was abrogated. iNKT cells enhance the proportion of a novel subset of multipotent, alloprimed CXCR3+CCR4+CD8+ cytolytic T cells that develop after hepatocyte transplant and are abundant in the liver. Alloprimed CXCR3+CCR4+CD8+ T cells express cytotoxic effector molecules (perforin/granzyme and Fas ligand) and are distinguished from alloprimed CXCR3+CCR4-CD8+ T cells by a higher proportion of cells expressing TNF-α and IFN-γ. Furthermore, alloprimed CXCR3+CCR4+CD8+ T cells mediate higher allocytotoxicity and more rapid allograft rejection. Our data demonstrate the important role of iNKT cells in promoting the development of highly cytotoxic, multipotent CXCR3+CCR4+CD8+ T cells that mediate rapid rejection of allogeneic hepatocytes engrafted in the liver. Targeting iNKT cells may be an efficacious therapy to prevent rejection of intrahepatic cellular transplants.

Triterpenoids of Rhus chinensis Supressed Colorectal Cancer Progress by Enhancing Antitumor Immunity and CD8 + T Cells Tumor Infiltration

The absence of CD8+ T cells in the tumor center has become a major obstacle in the immunotherapy of colorectal cancer. Therefore, new therapeutic strategies are urgently needed to promote the accumulation of CD8+ T cells in the tumor center. Previous studies have shown that triterpenoid of Rhus chinensis (TER) is involved in the proliferation and apoptosis of colorectal cancer cells, and can regulate their immune activity, but its mechanism needs to be further elucidated. In this study, the antitumor effect and adaptive immune response of TER on tumor-bearing mice were evaluated and compared with 5-fluorouracil. The results showed that TER could significantly inhibit tumor growth and prolong the survival time of tumor-bearing mice. The In Vivo studies have shown that TER can not only enhance antitumor immunity and promote the accumulation of CD8 + T cells to tumor sites, but also inhibit tumor progression by regulating the expression of PD-1 and PD-L1 and significantly reducing the mortality of mice. Our study demonstrated for the first time that TER has oncolytic effect, and recruited adaptive immune cells to enhance the efficacy of anti-PD-1/PD-L1 in colorectal cancer, which provides a potential therapeutic target for combined immunotherapy of colorectal cancer.

Structural Basis of Feedback Control of Oncogenic Signaling in B-Lymphoid Malignancies

Introduction: Multiple structural elements are known that recruit kinases to sites of active signal transduction (e.g. lipid rafts) within the plasma membrane. For instance, pleckstrin homology (PH) domains and the conserved intracellular loop (CIL) motifs recently discovered by us (Lee et al., Nature 2021) direct kinase molecules (Src, BTK, AKT and PI3K) to large signaling clusters in lipid rafts to amplify normal or oncogenic B-cell signaling. While concepts of site-specific recruitment of kinases to initiate signaling are well established, little is known about spatial control of inhibitory phosphatases and how they are directed to sites of maximal signaling strength.Results: Here we discovered the cytoplasmic tail of CD25 as an essential structural element for site-specific recruitment of inhibitory phosphatases. CD25-mediated shuttling of inhibitory phosphatases balances oncogenic signaling strength and is essential for cell-survival in B-cell malignancies, including B-ALL, CLL and mantle cell lymphoma. This was unexpected because CD25 (IL2RA) is known as one of three chains of the Interleukin-2 (IL2) receptor on T- and NK-cells. Studying clinical outcome and gene expression in multiple clinical cohorts, we found CD25 as a top-ranking predictor of poor clinical outcome in patients with B-ALL, mantle cell lymphoma and CLL.Our mechanistic experiments revealed that CD25 expressed on B-cells is monomeric. Unlike T- and NK-cells, CD25 expressed on activated or transformed B-cells does not form a heterotrimeric IL2 receptor with the IL2Rb and common g-chain. Instead of contributing to IL2-signaling, CD25 showed dynamic recruitment either to the B-cell receptor (BCR) or transforming oncogenes within lipid rafts. Conditional deletion of CD25 at earliest stages of B-cell development in mice resulted in profound B-cell defects. However, these defects were not replicated by IL2-deficiency and B-cell development in Il2-/- mice was normal.Inducible deletion of CD25 in genetic models for B-ALL and mantle cell lymphoma revealed an essential function of CD25 in maintaining homeostasis of signaling strength. In the absence of CD25, B-ALL and mantle cell lymphoma cells showed autonomous Ca 2+ oscillations, constitutive activation of Src-family kinases, BTK and ERK as well as the AMPK energy-stress sensor. CD25-deficient B-ALL and mantle cell lymphoma cells initially showed increased proliferation but rapidly died from exhaustion. Consistent with massive accumulation of p53, CD25-deficient B-ALL cells failed to form colonies and to initiate leukemia in transplant-recipient mice.Our mechanistic studies focused on the short (13 residues) cytoplasmic tale of CD25, which features a prominent serine/threonine kinase substrate motif. In vitro kinase assays for 62 candidate serine/threonine kinases revealed PKCd as top-ranking kinase and the serine residue 268 in the tail of CD25 as its principal substrate. The proximity-based labeling assays (BioID) revealed that the CD25 tail recruits PKCd and its adapter RACK1, which scaffold the inhibitory phosphatases SHIP1 and SHP1 for site-specific activation in lipid rafts (see Schematic). Consistent with these results, phospho-proteomic studies revealed that inducible deletion of CD25 resulted in acute inactivation of SHIP1 and SHP1 as well as the inhibitory RACK1 scaffold. Multiscale molecular dynamics (MD) simulations revealed that PKCd-mediated phosphorylation of the CD25-tail (S268) tightened interactions with RACK1 and SHIP1 and SHP1 phosphatases, whereas these interactions were destabilized when the CD25-tail was mutated (S268A).Conclusions: Mechanisms of site-specific recruitment of kinases for signal amplification have been extensively studied. However, structural elements that direct inhibitory phosphatases to sites of maximal signaling activity for feedback control remained largely unknown. Here we discovered a PKCd substrate motif in the cytoplasmic tail of CD25 (S268) as a central element to recruit inhibitory phosphatases, scaffolded by RACK1, to curb excessive signaling activity and energy expenditure. High expression levels of CD25 enable higher baseline activity of oncogenic signaling and are associated with poor patient-outcome. Our preclinical studies based on CD25-antibody-drug-conjugates (ADC) revealed that CD25 as a novel target in refractory B-ALL and mantle cell lymphoma. [Display omitted] DisclosuresWeinstock: SecuraBio: Consultancy; ASELL: Consultancy; Bantam: Consultancy; Abcuro: Research Funding; Verastem: Research Funding; Daiichi Sankyo: Consultancy, Research Funding; AstraZeneca: Consultancy; Travera: Other: Founder/Equity; Ajax: Other: Founder/Equity.

Abstract MP263: CD8+ T-cells Regulate Macrophage Recruitment And Retention After Myocardial Infarction

Heart failure is the number one reason for admission, with myocardial infarctions (MI) as the underlying etiology in of 70% cases. Macrophages facilitate cardiac healing after the MI. Resident macrophages die due to the initial ischemic event and are replaced by monocyte-derived macrophages. The adaptive immune system, including cytotoxic CD8+ T-cells, are known regulators of inflammation and are upregulated in the circulation and in the infarct after an MI. Previously we showed mice deficient in CD8+ T-cells were protected from adverse remodeling. We hypothesized that after an MI, CD8+ T-cells regulate the recruitment and retention of monocytes. To test our hypothesis, C57Bl6J (WT; n≥3/day post-MI) and mice deficient in CD8+ T-cells (CD8-/-; n≥3/day post-MI) underwent permanent occlusion and tissue was collected at post-MI days 0 (no MI), 1, 3, 7, and 14. Mac3 staining of the infarct was performed to determine the macrophage time course. Infarct tissue was analyzed by bulk RNAseq (n=3/day/genotype) to determine possible genetic regulators at post-MI days 1, 7, and 14. Data was clustered based on the genetic markers of macrophage subtypes identified in previous single cell genomic studies. Mac3 staining of WT mice showed macrophages begin to infiltrate as early as post-MI day 1, peaking at day 7, and beginning to reach baseline levels by day 14. Interestingly, CD8-/- mice had a delay in macrophage recruitment at day 1; however, by day 3 there was almost double the amount of macrophages compared to the WT group. While no differences were observed at day 7 post-MI, CD8-/- mice had elevated macrophages at post-MI day 14 compared to the WT mice. Based on the gene clusters, the infarct tissue of CD8-/- mice had increased markers of resident-like macrophages at post-MI days 7 and 14 compared to WT mice. Resident macrophages have been shown to be cardioprotective post-MI, suggesting a possible protective mechanism in CD8-/- mice. In conclusion, our data indicates that CD8+ T-cells influence cardiac remodeling over the post-MI time course by facilitating in macrophage recruitment and retention. Furthermore, in the absence of CD8+ T-cells, there was an increase in resident-like macrophages that could prove to point to a more favorable repopulation of cells post-MI.

Abstract 101: B1b Cell Homeostasis Is Maintained By Cd40 In Atherosclerosis

Background: The co-stimulatory CD40-CD40L dyad is an important driver of atherosclerosis. CD40 exerts divergent, cell-specific roles, which differentially impacts atherogenesis. Objectives: We here investigate the role of the most prominent CD40-expressing cell type, the CD40 + B cell, in atherosclerosis. Methods: B cell subset specific CD40-expression of patients with mild and severe coronary artery disease (CAD) was determined by mass-cytometry and correlated to CAD severity. Underlying mechanisms were revealed using CD19-CD40 flfl -ApoE -/- (CD40 BKO ) and CD40 flfl -ApoE -/- (CD40 BWT ) mice. Results: Patients with severe CAD had similar CD40 expression levels on most B cell subsets but showed a profound decrease in CD40 on B1 cells. This was associated with increased atherosclerotic plaque burden and decreased plaque fibrosis. Likewise, CD40 BKO mice exhibited an increased plaque area and a more advanced stage of atherosclerosis. Absence of B cell CD40 caused a decrease in immunoglobulin (Ig) producing cells, including germinal center-, plasma-, but especially B1 cells, thereby reducing levels of (anti-ox/MDA-LDL) IgM and (anti-ox/MDA-LDL) IgG. Interestingly, transcriptomics analysis revealed that the absence of CD40 on B1b cells in particular, caused altered gene expression pathways related to lipid uptake ( Cd36, Ldlr ), cellular stress and metabolism ( Nr4a1, Hif1a ), and cell death ( Naip5/6, Top1 ). Indeed, in vitro analysis showed that B1b CD40KO cells took up excessive amounts of ac/oxLDL, exhibited defective BCR signaling, and were prone to apoptosis, especially in hyperlipidemic conditions. Finally, transfer of wild-type B1b cells into CD40 BKO mice prevented the increase in atherosclerosis. Conclusions: We here show that CD40 is a critical modulator of B1 cell protective function in hypercholesterolemia and atherosclerosis.

The identification of tumor-infiltrating lymphocytes in patients with stomach cancer

Background. Stomach cancer (SC) is the 6th most common neoplasm among cancers (1 033 701 cases; 5.7%) and the 3rd most deadly cancer worldwide for men and women (782 685 deaths, 8.2%). SC therapy is a complex treatment associated with surgery, adjuvant chemotherapy, targeted therapy and immunotherapy with checkpoint inhibitors, nowadays. Despite the fact that the SC understanding has significantly increased within recent years, the prognosis still remains poor. In addition, very often the patients with the same stage of SC according to the international TNM classification of malignant tumors have different overall survival. Therefore, in order to improve survival rates, is necessary to understand the mechanisms of disease progression and to find new effective predictive factors. Besides many SC predictive factors, such as clinical and morphological characteristics (Lauren histologic type of tumor, degree of differentiation), biomarkers, deficient mismatch repair (dMMR), we have also revealed the positive correlation between the degree of tumor infiltration of tumor-infiltrating lymphocytes (TILs), especially with the spatial location of cell types (intratumoral or stromal cells), and the survival indicators of the patients with malignant neoplasms, recently. Moreover, TILs are the most significant predictive factors in patient survival rates than the TNM classification. At the same time, TILs predictive role in SC is still not clearly defined. Thus, the understanding of the degree of tumor infiltration of TILs depending on the spatial location would allow to determine the predictive significance, as well as to determine the direction of the immune reactions generating in patients with SC at the tissue level, depending on the risk and probability of progression. Aim. To study the predictive significance of intratumoral and stromal CD4+TILs, CD8+TILs and CD4+/CD8+TILs in patients with gastric adenocarcinoma. Materials and methods. From 2017 to 2018, 45 previously untreated patients with gastric adenocarcinoma (25 patients with stages IIII, 20 patients with stage IV) received surgical/combined treatment or independent chemotherapy, respectively, at the Blokhin National Medical Research Center of Oncology. The histological material was carried out before the treatment. Intratumoral (iTILs) and stromal (sTILs) values of CD4+TILs, CD8+TILs, CD4/CD8+TILs and the predictive significance in respect of overall survival and progression-free survival (PFS) were studied. Results. During the observation period (16.46.2 months) CD4+/CD8+iTILs were factors of poor prognosis concerning PFS in patients of the first group (p=0.035; odds ratio OR 3.264, 95% confidence interval CI). We also identified the statistically significant decrease in CD4+iTILs, CD8+iTILs, CD4+/CD8+iTILs and the absence of CD4+sTILs, CD8+sTILs, CD4+/CD8+sTILs in patients with metastatic SC (р=0.0003; р=0.000004; р=0.00001). Conclusion. The results show the positive predictive significance of CD4+sTILs, CD8+sTILs, CD4+/CD8+sTILs. At the same time, the increase of CD4+/CD8+iTILs reduces the PFS in patients with early and locally advanced SC.

From the Editor’s Desk…

From the Editor’s Desk…