Germinal Center Cells Research Articles

Altered Ratio of T Follicular Helper Cells to T Follicular Regulatory Cells Correlates with Autoreactive Antibody Response in Simian Immunodeficiency Virus-Infected Rhesus Macaques.

Individuals with chronic HIV-1 infection have an increased prevalence of autoreactive Abs. Many of the isolated HIV broadly neutralizing Abs from these individuals are also autoreactive. However, the underlying mechanism(s) that produce these autoreactive broadly neutralizing Abs remains largely unknown. The highly regulated coordination among B cells, T follicular helper (TFH) cells, and T follicular regulatory (TFR) cells in germinal centers (GCs) of peripheral lymphatic tissues (LTs) is essential for defense against pathogens while also restricting autoreactive responses. We hypothesized that an altered ratio of TFH/TFR cells in the GC contributes to the increased prevalence of autoreactive Abs in chronic HIV infection. We tested this hypothesis using a rhesus macaque (RM) SIV model. We measured the frequency of TFH cells, TFR cells, and GC B cells in LTs and anti-dsDNA and anti-phospholipid Abs from Indian RMs, with and without SIV infection. We found that the frequency of anti-dsDNA and anti-phospholipid Abs was much higher in chronically infected RMs (83.3% [5/6] and 66.7% [4/6]) than in acutely infected RMs (33.3% [2/6] and 18.6% [1/6]) and uninfected RMs (0% [0/6] and 18.6% [1/6]). The increased ratio of TFH/TFR cells in SIV infection correlated with anti-dsDNA and anti-phospholipid autoreactive Ab levels, whereas the frequency of TFR cells alone did not correlate with the levels of autoreactive Abs. Our results provide direct evidence that the ratio of TFH/TFR cells in LTs is critical for regulating autoreactive Ab production in chronic SIV infection and possibly, by extension, in chronic HIV-1 infection.

Uracil DNA Glycosylase of Gammaherpesvirus alters somatic hypermutation through error-free DNA repair

Abstract The gammaherpesviruses (gHV) which include human Epstein Barr virus (EBV), Kaposi’s sarcoma-associated herpesvirus (KSHV) and murine gammaherpesvirus 68 (MHV68) are associated with B cell malignancy including Burkitt lymphoma. All herpesvirus encode a viral homolog of the mammalian Uracil DNA-glycosylase (UNG) gene. In B cells, mammalian UNG plays a critical role in the antibody diversification processes of class switch recombination (CSR) and somatic hypermutation (SHM). UNG processes U:G mismatches created by activation-induced cytidine deaminase (AID) in an error-prone fashion to accomplish CSR and SHM. During primary infection, gHV expands in the germinal center B cells which actively express AID and undergo CSR and SHM. However, the function of viral UNG (vUNG) on viral pathogenesis and host genome integrity during the mutagenic germinal center reaction is an open question. Using a MHV68 mouse infection model we find that germinal center cells are the major viral targets during acute infection. Analysis of infected cells demonstrates significant overlap of vUNG and AID expression. Using a cell based hypermutation reporter assay, we find that host UNG supports error-prone repair and mutagenesis while vUNG results in only high-fidelity error-free repair of AID lesions. In vitro biochemical characterization finds several differences between vUNG and host UNG, including the ability of vUNG to bind abasic sites. These results demonstrate a differential ability of UNGs to support error-prone versus error-free repair. The finding that vUNG is expressed in germinal center cells suggest a novel mechanism whereby gammaherpesvirus can affect antibody diversification and B lymphocyte function.

Gammaherpesvirus infected B cells display abnormal repertoire

Abstract Gammaherpesviruses (γHV) are oncogenic viruses that establish lifelong latency in B cells. Chronic infection with human γHV, Kaposi’s sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV) is associated with the development of lymphoproliferative diseases, lymphomas and other types of cancer. The murine equivalent of human γHV, MHV68, is widely used as an animal model for γHV infection. Primary infection is associated with mucosal tissue replication, expansion in germinal center (GC) B cells and chronic persistence in host’s memory B cells. The GC compartment undergoes somatic hypermutation (SHM), class switch recombination (CSR) and repertoire selection which generate long lived antibody-secreting plasma cells and memory B cells. It is not clear what impact γHV infection has on B cell differentiation, affinity maturation and clonal proliferation. We isolated and comparatively analyzed the B cell repertoire of infected and non-infected GC cells from individual mice. This was done by sequencing repertoire from both the single cells and GC populations using NGS high-throughput sequencing. We determined the effect of infection on diversity, selection, mutagenesis and expansion of clones within the GC population of a mouse. Our data indicate that repertoire from MHV68 infected B cell are distinct from non-infected GC cells and is characterized by unique clones, repertoire bias and inappropriate expansion of certain clones. Moreover, both B cell populations share CDR3 variants only on minimum level. Thus, our findings demonstrate that viral infection cause a subversion of GC mutagenic and selective processes which result in a skewed repertoire.

A phase 1 study of ibrutinib in combination with R-ICE in patients with relapsed or primary refractory DLBCL

AbstractIn the postrituximab era, approximately half of the patients with relapsed or refractory (rel/ref) diffuse large B-cell lymphoma (DLBCL) fail to achieve a chemosensitive response to standard salvage therapy, and are thus ineligible to proceed to autologous stem cell transplantation with curative intent. The Bruton tyrosine kinase inhibitor ibrutinib demonstrates single-agent activity in rel/ref DLBCL, particularly of non–germinal center (non-GC) cell of origin. We conducted a single-center phase 1 study evaluating dose-escalated ibrutinib, in a 3-by-3 design, in combination with rituximab, ifosfamide, carboplatin, and etoposide (R-ICE) in physiologically transplant-eligible rel/ref DLBCL patients. Twenty-one patients have been treated and are evaluable for toxicity with no dose-limiting toxicities observed through expansion with ibrutinib at 840 mg daily at dose level 3. Of the 20 patients evaluable for response, per modern International Conference on Malignant Lymphoma criteria, 11 patients achieved complete remission (CR) and 7 patients achieved partial remission for an overall response rate of 90%. All evaluable patients with non-GC DLBCL achieved a metabolic CR. Ibrutinib in combination with R-ICE demonstrates tolerability and efficacy in rel/ref DLBCL, particularly of non-GC phenotype. This treatment program warrants further investigation in later-phase studies. This trial was registered at www.clinicaltrials.gov as #NCT02219737.

Role of B-cell receptors for B-cell development and antigen-induced differentiation.

B-cell development is characterized by a number of tightly regulated selection processes. Signals through the B-cell receptor (BCR) guide and are required for B-cell maturation, survival, and fate decision. Here, we review the role of the BCR during B-cell development, leading to the emergence of B1, marginal zone, and peripheral follicular B cells. Furthermore, we discuss BCR-derived signals on activated B cells that lead to germinal center and plasma cell differentiation.

T Follicular Helper Cell-Germinal Center B Cell Interaction Strength Regulates Entry into Plasma Cell or Recycling Germinal Center Cell Fate

Higher- or lower-affinity germinal center (GC) B cells are directed either to plasma cell or GC recycling, respectively; however, how commitment to the plasma cell fate takes place is unclear. We found that a population of light zone (LZ) GC cells, Bcl6loCD69hi expressing a transcription factor IRF4 and higher-affinity B cell receptors (BCRs) or Bcl6hiCD69hi with lower-affinity BCRs, favored the plasma cell or recycling GC cell fate, respectively. Mechanistically, CD40 acted as a dose-dependent regulator for Bcl6loCD69hi cell formation. Furthermore, we found that expression of intercellular adhesion molecule 1 (ICAM-1) and signaling lymphocytic activation molecule (SLAM) in Bcl6loCD69hi cells was higher than in Bcl6hiCD69hi cells, thereby affording more stable T follicular helper (Tfh)-GC B cell contacts. These data support a model whereby commitment to the plasma cell begins in the GC and suggest that stability of Tfh-GC B cell contacts is key for plasma cell-prone GC cell formation.

RETRACTED: Elevated levels of follicular T helper cells and their association with therapeutic effects in patients with chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is characterized by an abnormal expansion of mature B cells with variable progression. Follicular T helper (Tfh) cells help B cells differentiate into plasma cells or long-lived memory B cells in germinal centres (GCs). However, the role of Tfh cells in CLL is poorly understand, and whether it plays a critical role in disease progression in vivo is lacking. In this study, we investigate the dynamic change of circulating Tfh cells in peripheral blood from patients with CLL during the treatment periods to evaluate their utility to predict disease progression. Our findings revealed the expansion of circulating CD4+CXCR5+, CD4+ICOS+, CD4+PD-1+ and CD4+CXCR5+ICOS+PD-1+ (Tfh) cells but lower serum IL-21 levels and CD4+ T cell polarization not only to Tfh2 subtypes but also to Tfh17 subtypes in patients with CLL at pretreatment compared to patients with monoclonal B cell lymphocytosis (MBL) and healthy individuals, especially in those with advanced stage, which indicate these Tfh cells could be employed as a novel indicator for disease progression. Moreover, we observed significant correlations of Tfh17 and immunoglobulin heavy chain variable region (IGHV) mutation. Importantly, significantly decreased CD4+ICOS+, CD4+PD-1+ and Tfh cells were found after effective treatments, whereas a significantly high CD4+ICOS+, CD4+PD-1+ and Tfh cells were still found in those with progressive disease after treatments, suggesting that circulating CD4+ICOS+, CD4+PD-1+, Tfh cells could predict therapeutic effects.

Reduced lymphotoxin-beta production by tumour cells is associated with loss of follicular dendritic cell phenotype and diffuse growth in follicular lymphoma.

Cytokine production is essential for follicular dendritic cell (FDC) maintenance and organization of germinal centres. In follicular lymphoma, FDCs are often disarrayed and may lack antigens indicative of terminal differentiation. We investigated the in situ distribution of cells producing lymphotoxin‐beta (LTB), lymphotoxin‐alpha (LTA), and tumour necrosis factor‐alpha (TNFA) transcripts in human reactive lymph nodes and in follicular lymphomas with follicular or diffuse growth pattern. LTB was the cytokine most abundantly produced in germinal centres. LTB was present in nearly 90% of germinal centre cells whereas LTA and TNFA were detected in 30 and 50%, respectively. Moreover, the amount of LTB expressed in reactive germinal centre cells was 80‐fold higher than that of LTA and 20‐fold higher than that of TNFA. LTB‐positive cells were more numerous in the germinal centre dark zone, whereas expression of the FDC proteins CD21, CD23, VCAM, and CXCL13 was more intense in the light zone. Tumour cells of follicular lymphomas produced less LTB than reactive germinal centre cells. The results of the in situ study were confirmed by RT‐PCR; LTB was significantly more abundant in reactive lymph nodes than in follicular lymphoma, with the lowest values detected in predominantly diffuse follicular lymphoma. In neoplastic follicles, low production of LTB by tumour B cells was associated with weaker expression of CD21+/CD23+ by FDCs. Our findings detail for the first time the distribution of LTA‐, LTB‐, and TNFA‐producing cells in human reactive germinal centres and in follicular lymphoma. They suggest the possibility that impaired tumour‐cell LTB production may represent a determinant of FDC phenotype loss and for defective follicular organization in follicular lymphoma.

Cbl Ubiquitin Ligases Control B Cell Exit from the Germinal-Center Reaction

Selective expansion of high-affinity antigen-specific B cells in germinal centers (GCs) is a key event in antibody affinity maturation. GC B cells with improved affinity can either continue affinity-driven selection or exit the GC to differentiate into plasma cells (PCs) or memory B cells. Here we found that deleting E3 ubiquitin ligases Cbl and Cbl-b (Cbls) in GC B cells resulted in the early exit of high-affinity antigen-specific B cells from the GC reaction and thus impaired clonal expansion. Cbls were highly expressed in GC light zone (LZ) B cells, where they promoted the ubiquitination and degradation of Irf4, a transcription factor facilitating PC fate choice. Strong CD40 and BCR stimulation triggered the Cbl degradation, resulting in increased Irf4 expression and exit from GC affinityselection. Thus, a regulatory cascade that is centered on the Cbl ubiquitin ligases ensures affinity-driven clonal expansion by connecting BCR affinity signals with differentiation programs.

Increased circulating CD4+CXCR5+FoxP3+ follicular regulatory T cells correlated with severity of systemic lupus erythematosus patients

As one specialized subset of regulatory T cells (Tregs), follicular regulatory T cells (TFR) could suppress follicular helper T cells (TFH) and B cells in germinal centers to maintain immune homeostasis. The unbalance of TFR and TFH cells could result in abnormal germinal center responses and contribute to pathogenesis of autoimmune diseases. However, the role of TFR cells in systemic lupus erythematosus (SLE) remains unclear. This study revealed a significant increase of CD4+CXCR5+FOXP3+ TFR cells in peripheral blood of SLE patients compared with healthy controls. Meanwhile, the suppression ability of circulating TFR cells was not altered. The ratios of TFR/TFH were increased in SLE patients and the frequency of TFR was positively correlated with auto-antibodies and SLEDAI scores of SLE patients. Our results demonstrated that circulating TFR cells were increased during SLE, which suggested that elevated TFR might be a response to the pathogenesis of SLE to suppress TFH function and may provide novel insight for the pathogenesis of SLE.

The B-Cell Follicle in HIV Infection: Barrier to a Cure.

The majority of HIV replication occurs in secondary lymphoid organs (SLOs) such as the spleen, lymph nodes, and gut-associated lymphoid tissue. Within SLOs, HIV RNA+ cells are concentrated in the B-cell follicle during chronic untreated infection, and emerging data suggest that they are a major source of replication in treated disease as well. The concentration of HIV RNA+ cells in the B-cell follicle is mediated by several factors. Follicular CD4+ T-cell subsets including T-follicular helper cells and T-follicular regulatory cells are significantly more permissive to HIV than extrafollicular subsets. The B cell follicle also contains a large reservoir of extracellular HIV virions, which accumulate on the surface of follicular dendritic cells (FDCs) in germinal centers. FDC-bound HIV virions remain infectious even in the presence of neutralizing antibodies and can persist for months or even years. Moreover, the B-cell follicle is semi-immune privileged from CTL control. Frequencies of HIV- and SIV-specific CTL are lower in B-cell follicles compared to extrafollicular regions as the majority of CTL do not express the follicular homing receptor CXCR5. Additionally, CTL in the B-cell follicle may be less functional than extrafollicular CTL as many exhibit the recently described CD8 T follicular regulatory phenotype. Other factors may also contribute to the follicular concentration of HIV RNA+ cells. Notably, the contribution of NK cells and γδ T cells to control and/or persistence of HIV RNA+ cells in secondary lymphoid tissue remains poorly characterized. As HIV research moves increasingly toward the development of cure strategies, a greater understanding of the barriers to control of HIV infection in B-cell follicles is critical. Although no strategy has as of yet proven to be effective, a range of novel therapies to address these barriers are currently being investigated including genetically engineered CTL or chimeric antigen receptor T cells that express the follicular homing molecule CXCR5, treatment with IL-15 or an IL-15 superagonist, use of bispecific antibodies to harness the killing power of the follicular CD8+ T cell population, and disruption of the follicle through treatments such as rituximab.

Tuning of in vivo cognate B-T cell interactions by Intersectin 2 is required for effective anti-viral B cell immunity.

Wiskott-Aldrich syndrome (WAS) is an immune pathology associated with mutations in WAS protein (WASp) or in WASp interacting protein (WIP). Together with the small GTPase Cdc42 and other effectors, these proteins participate in the remodelling of the actin network downstream of BCR engagement. Here we show that mice lacking the adaptor protein ITSN2, a G-nucleotide exchange factor (GEF) for Cdc42 that also interacts with WASp and WIP, exhibited increased mortality during primary infection, incomplete protection after Flu vaccination, reduced germinal centre formation and impaired antibody responses to vaccination. These defects were found, at least in part, to be intrinsic to the B cell compartment. In vivo, ITSN2 deficient B cells show a reduction in the expression of SLAM, CD84 or ICOSL that correlates with a diminished ability to form long term conjugates with T cells, to proliferate in vivo, and to differentiate into germinal centre cells. In conclusion, our study not only revealed a key role for ITSN2 as an important regulator of adaptive immune-response during vaccination and viral infection but it is also likely to contribute to a better understanding of human immune pathologies.

Competitive Treatment in Diffuse Large B-cell lymphoma (DLBCL) and the Future SOC for the First Line Therapy

Diffuse large B-cell lymphoma (DLBCL) in the most common type of non-Hodgkin’s lymphoma (NHL) in developed world, so far and approximately 60,000 new non-Hodgkin lymphoma (NHL) cases and 20,000 deaths have been estimated in the United States for 2010. In spite of novel therapeutic options have been suggested and successfully tried in patients with lymphoproliferative disorders, the standard first- line treatment for DLBCL has remained the same combination of chemotherapy and CD20 (activated-glycosylated phosphoprotein) targeting monoclonal antibody rituximab (R) with 30% to 40% chance of relapse after first line R-CHOP treatment. Several clinical trials have been designed to evaluate safety, efficacy and superior clinical benefit by adding novel agents, intensifying cycles of treatment or substituting rituximab with new CD20 targeting immunotherapies. Intensification of cyclophosphamide, doxorubicin, vincristine, prednisone (CHOP) chemotherapy from 3- week interval cycles to 2- week interval cycles has already shown clinical benefit in a German trial but failed to show improved overall and disease free (DFS1) survival in both elderly (60 to 80 years) and young patients in randomized phase 3 clinical trials. Namely, in a phase 2 randomized clinical trials (PYRAMID) as a first line treatment for non- Germinal Center Cell (GCB) subtype of DLBCL the results were in favor of R-CHOP and adding bortezomib was not found to improve DFS and OS significantly. Immunomodulatory agent lenalidomide is another attractive therapeutic option for non-GCB subtype of DLBCL. Statistically significant difference between non-GCB and GCB controls treated with standard R-CHOP alone in terms of progression-free survival (28% vs. 64%; P = 0.00029) and overall survival (46% vs. 74%; P = 0.000036) was reported while non-GCB and GCB treated with R-CHOP plus lenalidomide had similar rates of progression (60% vs. 59%; P = 0.83) and overall survival at 2 years (83% vs. 75%; P = 0.61). Despite these promising clinical results, further clinical studies, especially phase 3 randomized clinical trials are required to confirm the alternate competitive treatment for DLBCL patients.

Live Imaging of IL-4-Expressing T Follicular Helper Cells in Explanted Lymph Nodes.

The generation of class-switched, high-affinity, antibody-producing B cells plays a critical role in the establishment of type 2 immunity to intestinal helminths as well as in the pathogenesis of allergy and asthma. The generation of these high-affinity, antibody-producing B cells occurs in germinal centers (GC) and relies on interactions with follicular dendritic cells (FDCs) and T follicular helper (Tfh) cells. One critical mediator produced by Tfh cells in GCs is interleukin-4 (IL-4). Tfh-derived IL-4 drives class switching to type 2 antibody isotypes IgE and IgG1 and is required for high-affinity IgG1 production. In vivo detection of IL-4-expressing Tfh cells is required to better understand the role of these cells during the GC response. Detection of IL-4-expressing cells has been greatly improved by the generation of the IL-44get reporter mice, which read out IL-4 expression as green fluorescent protein (GFP). Much has been learned from these mice with regard to type 2 immunity using flow cytometry and immunohistochemistry. However, these methods do not allow the study of cellular behavior and interactions in real time. In contrast, multi-photon microscopy allows for deep tissue imaging and tracking of multiple cell types in intact tissues over time. Here, we describe a protocol for in vivo detection of IL-4-expressing Tfh cells in an explanted popliteal lymph node by multi-photon microscopy. The dynamics of Tfh cell motility and their interactions with FDC networks in the GCs were analyzed.

HIV Immunogens: Affinity Is Key

Generation of broadly neutralizing antibodies is a key aim of HIV vaccine design, but the precursor B cells are rare. Abbott etal. (2018) report that high affinity and avidity immunogens are required to promote maturation of low frequency B cells in germinal centers.

Mer Receptor Tyrosine Kinase Signaling Prevents Self-Ligand Sensing and Aberrant Selection in Germinal Centers.

Mer tyrosine kinase (Mer) signaling maintains immune tolerance by clearing apoptotic cells (ACs) and inducing immunoregulatory signals. We previously showed that Mer-deficient mice (Mer-/-) have increased germinal center (GC) responses, T cell activation, and AC accumulation within GCs. Accumulated ACs in GCs can undergo necrosis and release self-ligands, which may influence the outcome of a GC response and selection. In this study, we generated Mer-/- mice with a global MyD88, TLR7, or TLR9 deficiency and cell type-specific MyD88 deficiency to study the functional correlation between Mer and TLRs in the development of GC responses and autoimmunity. We found that GC B cell-intrinsic sensing of self-RNA, but not self-DNA, released from dead cells accumulated in GCs drives enhanced GC responses in Mer-/- mice. Although self-ligands directly affect GC B cell responses, the loss of Mer in dendritic cells promotes enhanced T cell activation and proinflammatory cytokine production. To study the impact of Mer deficiency on the development of autoimmunity, we generated autoimmune-prone B6.Sle1b mice deficient in Mer (Sle1bMer-/-). We observed accelerated autoimmunity development even under conditions where Sle1bMer-/- mice did not exhibit increased AC accumulation in GCs compared with B6.Sle1b mice, indicating that Mer immunoregulatory signaling in APCs regulates B cell selection and autoimmunity. We further found significant expansion, retention, and class-switching of autoreactive B cells in GCs under conditions where ACs accumulated in GCs of Sle1bMer-/- mice. Altogether, both the phagocytic and immunomodulatory functions of Mer regulate GC responses to prevent the development of autoimmunity.

Abstract 30: SOX9 enhancer regulator may play an oncogenic role in B-cell lymphomas

Abstract A majority of B-cell lymphomas, including diffuse large B-cell lymphomas (DLBCLs) and follicular lymphomas (FLs), arise from germinal center (GC) B cells. GC B cells are highly proliferative and manifest genomic instability as a byproduct of immunoglobulin affinity maturation. These characteristics make GC B cells particularly prone to malignant transformation such that DLBCLs and FLs inherit and are dependent on mutations in proteins that are also required for normal GC B cells. For example, the BCL6 transcriptional repressor is required to establish the GC phenotype in both normal B-cell development and GC B-cell malignancy through its effect on silencing expression of plasma cell differentiation and checkpoint genes. GC B cells feature a unique transcriptional program featuring upregulation of genes involved in cell proliferation and other growth pathways. Cell context-specific gene expression is largely mediated through gene enhancers. Hence we hypothesized that transcription factors that activate GC specific gene enhancers would play a critical role in formation of these cells, and would likely be required in turn to maintain the survival of GC-derived lymphoma cells. To address this question we first mapped gene enhancers in primary human resting B cells and purified GC B cells by performing ChIP-seq to map the distribution of H3K27Acetyl, H3K4me1, and H3K4me3. This procedure allowed us to identify several thousand GC-specific enhancers. We next examined these enhancers using bioinformatic approaches to identify transcription factor binding sites and identified a list of fifteen putative GC enhancer regulators. Of these potential GC enhancer regulators, only SOX9 was highly induced in GC B cells as compared to resting B cells, pointing to SOX9 as a candidate master enhancer regulator of the GC transcriptome with potential relevance to lymphomas. Indeed, in addition to the well-known role of SOX9 as a stem cell self-renewal and cell-differentiation regulator during development, SOX9 has also been described as playing a role in colon, breast, and prostate carcinogenesis through inhibition of apoptosis, and promoting proliferation, invasion, and metastasis. We confirmed that SOX9 is highly induced in GC cells using QPCR and Western blots. To determine whether SOX9 would indeed bind to these enhancer sites, we next performed SOX9 ChIP-seq in GC B-cell derived lymphoma cell lines. These experiments validated and showed that SOX9 binds to 1,668 upstream distal enhancer regions (-5 to -100 kb upstream from TSS) associated with 963 genes. These target genes were significantly enriched in cell cycle regulation (CCND2, CDC25B, CDK1), transcription regulation (BCOR, NCOR2), epigenetic regulation (BMI1, DNMT3A, MLL2, SUZ12, TET3), and MAPK signaling (MAP2K3, MAP3K7) and also for B-cell activation and BCL6 repressed pathways (p<0.001). We next wished to determine whether SOX9 was also expressed in GC-derived lymphoma clinical samples. Therefore we next examined RNA-seq gene expression profiles derived from cohorts of FL and DLBCL patients. We found that SOX9 is expressed at higher levels in FL patient samples, but lower levels in most DLBCLs compared to naïve B cells. These data raise the possibility that SOX9 might be differentially relevant to FL more than DLBCLs, perhaps contributing to the biologic distinction between these two GC-derived lymphomas. To determine if SOX9 protein was also expressed in these tumors, we examined protein expression by immunohistochemistry using tissue microarrays (TMAs) containing both FLs and DLBCLs. We found that 88 of the 242 FL TMA samples (36.4%) were positive for SOX9 staining. Eleven of the 114 DLBCL TMA samples (10%) were positive for SOX9 staining, among which 80% (9/11) were GC-type DLBCL and 45% (5/11) had a prior FL history. To determine if any of the currently available GC derived lymphoma cell lines manifest high SOX9 levels, we performed a series of Western blot experiments. These studies show high levels of SOX9 protein in the GC-type DLBCL cell lines HT, Karpas422, DB, and Farage, but not in any of the eight ABC-DLBCLs subtypes. Ongoing studies are assessing the biologic relevance of SOX9 for the GC reaction and possible contribution to lymphomagenesis using gain- and loss-of-function studies in human cells and mouse models. These data will determine whether this apparently key enhancer regulatory protein is a novel lineage factor for follicular lymphoma and potentially suitable as a therapeutic target. Citation Format: Angela A. Fachel, Yanwen Jiang, Wayne Tam, Ashlesha S. Muley, Cem Meydan, Xabier Agirre, Ari M. Melnick, Kristy L. Richards. SOX9 enhancer regulator may play an oncogenic role in B-cell lymphomas [abstract]. In: Proceedings of the Second AACR Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; May 6-9, 2017; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(24_Suppl):Abstract nr 30.

Abstract IA21: Immunomodulatory therapy of multiple myeloma with IAP antagonists

Abstract IA21: Immunomodulatory therapy of multiple myeloma with IAP antagonists

Initiation of Antiviral B Cell Immunity Relies on Innate Signals from Spatially Positioned NKT Cells

SummaryB cells constitute an essential line of defense from pathogenic infections through the generation of class-switched antibody-secreting cells (ASCs) in germinal centers. Although this process is known to be regulated by follicular helper T (TfH) cells, the mechanism by which B cells initially seed germinal center reactions remains elusive. We found that NKT cells, a population of innate-like T lymphocytes, are critical for the induction of B cell immunity upon viral infection. The positioning of NKT cells at the interfollicular areas of lymph nodes facilitates both their direct priming by resident macrophages and the localized delivery of innate signals to antigen-experienced B cells. Indeed, NKT cells secrete an early wave of IL-4 and constitute up to 70% of the total IL-4-producing cells during the initial stages of infection. Importantly, the requirement of this innate immunity arm appears to be evolutionarily conserved because early NKT and IL-4 gene signatures also positively correlate with the levels of neutralizing antibodies in Zika-virus-infected macaques. In conclusion, our data support a model wherein a pre-TfH wave of IL-4 secreted by interfollicular NKT cells triggers the seeding of germinal center cells and serves as an innate link between viral infection and B cell immunity.

Linfoma cutáneo primario de células B centrofolicular: un desafío diagnóstico

El linfoma cutáneo primario de células B (LCPCB) centrofolicular corresponde a una proliferación neoplásica infrecuente e indolente de células del centro germinal confinadas a la piel. Se reporta y revisa un caso de LCPCB centrofolicular.Paciente femenino de 76 años, con antecedentes de hipertensión arterial y resistencia a la insulina. Consultó por aumento de volumen frontal de dos años de evolución. Al examen físico destacaba un nódulo único en región frontal derecha. La ecografía de partes blandas fue compatible con quiste epidérmico. La histopatología demostró en dermis profunda, tejido adiposo subcutáneo y tejido muscular estriado una proliferación linfoide sólida dispuesta en patrón nodular y difuso. A la inmunohistoquímica (IHQ), los linfocitos fueron CD20 y BCL-6 positivo, con un Ki-67 de 60% y BCL-2, CD3, CD5 y CD10 negativo. El estudio de diseminación tumoral resultó negativo. El LCPCB centrofolicular concentra el 60% de todos los LCPCB. Se presenta en promedio a los 51 años. Se ha descrito asociación con Borrelia burgdorferi, VIH, virus hepatitis C y virus Epstein-Barr. Clínicamente corresponde a un nódulo eritematoso y asintomático, localizado preferentemente en cabeza, cuello y tronco. La IHQ es fundamental para diferenciarlo de otros tipos de LCPCB. Habitualmente, el tratamiento es con radioterapia o cirugía escisional. La supervivencia es de un 95% a 5 años. Se presenta este caso dado que el LCPCB centrofolicular corresponde a un tumor cutáneo infrecuente, con múltiples diagnósticos diferenciales, que requiere de un alto índice de sospecha para lograr un diagnóstico y tratamiento oportuno.