STAT3 Mutations Research Articles

Epstein-Barr virus and immune status imprint the immunogenomics of non-Hodgkin lymphomas occurring in immune-suppressed environments.

Non-Hodgkin lymphomas (NHL) commonly occur in immunodeficient patients, both those infected by human immunodeficiency virus (HIV) and those who have been transplanted, and are often driven by Epstein-Barr virus (EBV) with cerebral localization, raising the question of tumor immunogenicity, a critical issue for treatment responses. We investigated the immunogenomics of 68 lymphoproliferative disorders from 51 immunodeficient (34 post-transplant, 17 HIV+) and 17 immunocompetent patients. Overall, 72% were large B-cell lymphoma and 25% were primary central nervous system lymphoma, while 40% were EBV+. Tumor whole-exome and RNA sequencing, along with a bioinformatics pipeline allowed analysis of tumor mutational burden, tumor landscape and tumor microenvironment and prediction of tumor neoepitopes. Both tumor mutational burden (2.2 vs. 3.4/Mb, P=0.001) and numbers of neoepitopes (40 vs. 200, P=0.00019) were lower in EBV+ than in EBV- NHL, regardless of the immune status. In contrast both EBV and the immune status influenced the tumor mutational profile, with HNRNPF and STAT3 mutations observed exclusively in EBV+ and immunodeficient NHL, respectively. Peripheral blood T-cell responses against tumor neoepitopes were detected in all EBV- cases but in only half of the EBV+ ones, including responses against IgH-derived MHC-class-II restricted neoepitopes. The tumor microenvironment analysis showed higher CD8 T-cell infiltrates in EBV+ versus EBV- NHL, together with a more tolerogenic profile composed of regulatory T cells, type-M2 macrophages and an increased expression of negative immune-regulators. Our results highlight that the immunogenomics of NHL in patients with immunodeficiency primarily relies on the tumor EBV status, while T-cell recognition of tumor- and IgH-specific neoepitopes is conserved in EBV- patients, offering potential opportunities for future T-cell-based immune therapies.

Activating STAT3 mutations in CD8+ T-cells correlate to serological positivity in rheumatoid arthritis.

Large granular lymphocyte (LGL) leukemia is a rare hematologic malignancy characterized by clonal expansion of cytotoxic T-cells frequent somatic activating STAT3 mutations. Based on the disease overlap between LGL leukemia rheumatoid arthritis (RA)a putative role for CD8+ T-cells in RA we hypothesized that STAT3 mutations may be detected in RA patient CD8+ T-cells correlate with clinical characteristics. Blood samples, clinical parameters, and demographics were collected from 98 RA patients and 9 healthy controls (HCs). CD8+ cell DNA was isolated and analyzed via droplet digital (dd)PCR to detect STAT3 mutations common in LGL leukemia: Y640F, D661Y, and the S614 to G618 region. STAT3 data from 99 HCs from a public dataset supplemented our 9 HCs. RA patients had significantly increased presence of STAT3 mutations compared to controls (Y640F p=0.0005, D661Y p=0.0005). The majority of these were low variant allele frequency (VAF) (0.008-0.05%) mutations detected in a higher proportion of the RA population (31/98 Y640F, 17/98 D661Y) vs. HCs (0/108 Y640F, 0/108 D661Y). In addition, 3/98 RA patients had a STAT3 mutation at a VAF >5% compared to 0/108 controls. Serological markers, RF and anti-CCP positivity, were more frequently positive in RA patients with STAT3 mutation relative to those without (88% vs 59% RF, p=0.047; 92% vs 58% anti-CCP, p=0.031, respectively). STAT3 activating mutations were detected in RA patient CD8+ cells and associated with seropositivity. Thus, STAT3 activating mutations may play a role in disease pathogenesis in a subset of RA patients.

Composite Lymphoma Comprising of BCL2 Rearrangement Negative, CD23 Positive Follicle Center Cell Lymphoma and Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma: A Case Report

Abstract Introduction/Objective BCL2 rearrangement negative, CD23-positive follicle center cell lymphoma (BCL2 neg CD23 pos FCL) is a rare, recently described provisional entity in International Consensus Classification (2022). It has a predominantly diffuse growth pattern and often involves inguinal region. The molecular profile includes a high frequency of STAT6 and CREBBP co-mutation as well as 1q gain and a recurrent 1p36 loss/TNFRS14 abnormalities. We describe a composite tumor comprising of a rare entity BCL2 neg CD23 pos FCL and Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL). To the best of our knowledge this is the first reported case description of this co-occurrence. Methods/Case Report A 59 y/o woman presented with right cervical and axillary lymphadenopathy (upto 1.6 cm). Sections showed partial effacement of nodal architecture by interfollicular and diffuse proliferation of atypical lymphoid cells. The interfollicular areas were comprised of a monotonous population of small lymphocytes. Immunohistochemical stains performed showed that the interfollicular CD20+ PAX5+ atypical lymphoid cells coexpressed CD5, CD23, BCL2 and LEF1 and were negative for CD10, BCL6, CD3, and SOX11, with MIB1 of 5-10%. Based on these, a diagnosis of CLL/SLL was made. Admixed with the CLL/SLL, a second neoplastic B-cell component that distorted nodal architecture was also identified. It composed of a diffuse proliferation of intermediate sized lymphoid cells with a centrocytic/centroblastic morphology. This smaller population of small to intermediate sized B cells expressed CD10, BCL6, and CD23 with a MIB1 proliferation index of ~30%. This population was CD5 and BCL2 negative. CD21 showed residual follicular dendritic cell meshworks. SOX11 and BCL1 were negative. Therefore, a diagnosis of BCL2 neg CD23 pos FCL was made. Flow cytometry showed two distinct populations of monotypic B-cells, one CD5-positive and the other CD10-positive. FISH studies were negative for BCL2 and BCL6 rearrangements as well as del1p36. Cytogenetics was positive for trisomy 12, supporting CLL/SLL. Next Generation Sequencing showed Tier 1 / 2 mutations in STAT6, TNFRSF14, CREBBP, and FOXO1, supporting BCL2 neg CD23 pos FCL. Hence, this represents a unique case of composite CLL/SLL and BCL2 neg CD23 pos FCL. B cell gene rearrangement showed 2 distinct clones confirming 2 separate B cell lymphomas. Results (if a Case Study enter NA) NA Conclusion Here, we describe a composite CLL/SLL and BCL2 rearrangement negative, CD23 positive, FCL never previously described in literature.

Identification of a stat3 mutation, P.THR716MET in two cases of very early-onset autoimmune hypothyroidism

Identification of a stat3 mutation, P.THR716MET in two cases of very early-onset autoimmune hypothyroidism

Unraveling the unphosphorylated STAT3-unphosphorylated NF-κB pathway in loss of function STAT3 Hyper IgE syndrome.

Patients with loss of function signal transducer and activator of transcription 3-related Hyper IgE Syndrome (LOF STAT3 HIES) present with recurrent staphylococcal skin and pulmonary infections along with the elevated serum IgE levels, eczematous rashes, and skeletal and facial abnormalities. Defective STAT3 signaling results in reduced Th17 cells and an impaired IL-17/IL-22 response primarily due to a compromised canonical Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway that involves STAT3 phosphorylation, dimerization, nuclear translocation, and gene transcription. The non-canonical pathway involving unphosphorylated STAT3 and its role in disease pathogenesis, however, is unexplored in HIES. This study aims to elucidate the role of unphosphorylated STAT3-unphosphorylated NF-κB (uSTAT3-uNF-κB) activation pathway in LOF STAT3 HIES patients. The mRNA expression of downstream molecules of unphosphorylated STAT3-unphosphorylated NF-κB pathway was studied in five LOF STAT3 HIES patients and transfected STAT3 mutants post-IL-6 stimulation. Immunoprecipitation assays were performed to assess the binding of STAT3 and NF-κB to RANTES promoter. A reduced expression of the downstream signaling molecules of the uSTAT3-uNF-κB complex pathway, viz., RANTES, STAT3, IL-6, IL-8, ICAM1, IL-8, ZFP36L2, CSF1, MRAS, and SOCS3, in LOF STAT3 HIES patients as well as the different STAT3 mutant plasmids was observed. Immunoprecipitation studies showed a reduced interaction of STAT3 and NF-κB to RANTES in HIES patients. The reduced expression of downstream signaling molecules, specially RANTES and STAT3, confirmed the impaired uSTAT3-uNF-κB pathway in STAT3 LOF HIES. Decreased levels of RANTES and STAT3 could be a significant component in the disease pathogenesis of Hyper IgE Syndrome.

Dysregulated Airway Host Defense in Hyper IgE Syndrome due to STAT3 Mutations.

Hyper IgE syndrome (STAT3-HIES), also known as Job's syndrome, is a rare immunodeficiency disease typically caused by dominant-negative STAT3 mutations. STAT3-HIES syndrome is characterized by chronic pulmonary infection and inflammation, suggesting impairment of pulmonary innate host defense. To identify airway epithelial host defense defects consequent to STAT3 mutations that, in addition to reported mutant STAT3 immunologic abnormalities, produce pulmonary infection. STAT3-HIES sputum was evaluated for biochemical/biophysical properties. STAT3-HIES excised lungs were harvested for histology; bronchial brush samples were collected for RNA sequencing and in vitro culture. A STAT3-HIES-specific mutation (R382W), expressed by lentiviruses, and a STAT3 knockout, generated by CRISPR/Cas9, were maintained in normal human bronchial epithelia under basal or inflammatory (IL1β) conditions. Effects of STAT3 deficiency on transcriptomics, and epithelial ion channel, secretory, antimicrobial, and ciliary functions were assessed. Mucus concentrations and viscoelasticity were increased in STAT3-HIES sputum. STAT3-HIES excised lungs exhibited mucus obstruction and elevated IL1β expression. STAT3 deficiency impaired CFTR-dependent fluid and mucin secretion, inhibited expression of antimicrobial peptides, cytokines, and chemokines, and acidified airway surface liquid at baseline and post-IL1β exposure in vitro. Notably, mutant STAT3 suppressed IL1R1 expression. STAT3 mutations also inhibited ciliogenesis in vivo and impaired mucociliary transport in vitro, a process mediated via HES6 suppression. Administration of a γ-secretase inhibitor increased HES6 expression and improved ciliogenesis in STAT3 R382W mutant cells. STAT3 dysfunction leads to multi-component defects in airway epithelial innate defense, which, in conjunction with STAT3-HIES immune deficiency, contributes to chronic pulmonary infection.

Dissecting Out a Rare Mutation, STAT: Features of STAT3-Mutant Myeloid Neoplasms.

The transcription factor STAT3 drives the expression of genes promoting cellular proliferation, survival, and pluripotency. The description of STAT3 mutations and their clinical correlates in myeloid neoplasms, such as acute myeloid leukemia and myelodysplastic syndromes, raises new insights into both the pathogenesis and the targeted therapy of these diseases. See related article by Ye et al., p. 4681.

Gamma-delta T-cell large granular lymphocytic leukemia in the setting of rheumatologic diseases.

T-cell leukemia originating from large granular lymphocytes (T-LGL leukemia) is a rare lymphoid neoplasia characterized by clonal proliferation of large granular T lymphocytes expressing αβ or γδ T-cell receptor (TCR) on the cell membrane. γδT-LGL leukemia, accounting for approximately 17% of all T-LGL leukemia cases, is associated with autoimmune diseases. However, the features of γδT-LGL leukemia in patients with rheumatologic diseases are still insufficiently characterized. In this retrospective study, 15 patients with rheumatologic disease-associated γδT-LGL leukemia were included. The patients were obtained from a single center from 2008 to 2023. Data related to clinical characteristics and rheumatologic diagnoses were collected. Immunophenotype evaluations as well as T-lymphocyte clonality (based on TCR-γ, TCR-β, and TCR-δ gene rearrangements), and signal transducer and activator of transcription (STAT) three and STAT5B mutation analyses (by next-generation sequencing) were performed on blood, bone marrow, and spleen samples. All but one patient had rheumatoid arthritis (RA). In 36% of patients, manifestations of γδT-LGL leukemia were present before or concurrently with clinical manifestations of RA. Splenomegaly was observed in 60% of patients and neutropenia (<1.5 × 109/L) was detected in 93% of cases. CD4-/CD8- and CD4-/CD8+ subtypes were detected in seven cases each. Mutations in STAT3 were detected in 80% of patients; however, STAT5B mutations were not detected. Evaluations of T-cell clonality and variant allele frequencies at STAT3 in the blood, bone marrow, and spleen tissue revealed an unusual variant of CD4-/CD8- γδT-LGL leukemia with predominant involvement of the spleen, involvement of the bone marrow to a less extent, and no tumor cells in peripheral blood. The mechanism by which γδT-LGL leukemia may induce the development of RA in some patients requires further investigation. Cases of RA-associated γδT-LGL leukemia with neutropenia and splenomegaly but no detectable tumor-associated lymphocytes in peripheral blood (the so-called splenic variant of T-LGL leukemia) are difficult to diagnose and may be misdiagnosed as Felty syndrome or hepatosplenic T-cell lymphoma.

Hyper IgE Syndromes.

The Hyper IgE Syndromes are rare primary immunodeficiencies characterized by eczema, recurrent skin and respiratory infections and elevated serum IgE levels. Nowadays a geneticmolecular characterization is possible and allows the distinction in various monogenic pathologies, which share some clinical characteristics but also important differences. In addition to long-known STAT3 and DOCK8 gene mutations, in fact, also ZNF341, CARD11, ERBB2IP, IL6R and IL6ST genes mutations can cause the disease. The main clinical manifestations are represented by newborn rash, eczema similar to atopic dermatitis, bacterial and viral skin infections, cold abscesses, respiratory infections with possible pulmonary complications, allergies, gastrointestinal manifestations, malignancies and connective tissue abnormalities. Diagnosis is still a challenge because, especially in the early stages of life, it is difficult to distinguish from other pathologies characterized by eczema and high IgE, such as atopic dermatitis. Several scores and diagnostic pathways have been developed, but it is essential to seek a genetic diagnosis. Treatment is based on prevention and early treatment of infections, meticulous skincare, intravenous immunoglobulins and HSCT, which, in some HIES subtypes, can modify the prognosis. Prognosis is related to the affected gene, but also to early diagnosis, timely treatment of infections and early HSCT.

STAT3 gain of function: Too much of a good thing in the skin!

Germline activating mutations in STAT3 cause a multi-systemic autoimmune and autoinflammatory condition. By studying a mouse model, Toth et al. (https://doi.org/10.1084/jem.20232091) propose a role for dysregulated IL-22 production by Th17 cells in causing some aspects of immune-mediated skin inflammation in human STAT3 GOF syndrome.

Transformation of t(14;18)-negative follicular lymphoma to plasmablastic lymphoma: a case report with analysis of genetic evolution

BackgroundFollicular lymphoma (FL) is characterized by t(14;18)(q32;q21) involving the IGH and BCL2 genes. However, 10–15% of FLs lack the BCL2 rearrangement. These BCL2-rearrangement−negative FLs are clinically, pathologically, and genetically heterogeneous. The biological behavior and histological transformation of such FLs are not adequately characterized. Here, we report the first case of t(14;18)-negative FL that rapidly progressed to plasmablastic lymphoma (PBL).Case presentationA previously healthy 51-year-old man presented with leg swelling. Computed tomography (CT) showed enlarged lymph nodes (LNs) throughout the body, including both inguinal areas. Needle biopsy of an inguinal LN suggested low-grade B-cell non-Hodgkin lymphoma. Excisional biopsy of a neck LN showed proliferation of centrocytic and centroblastic cells with follicular and diffuse growth patterns. Immunohistochemical analysis showed that the cells were positive for CD20, BCL6, CD10, and CD23. BCL2 staining was negative in the follicles and weak to moderately positive in the interfollicular areas. BCL2 fluorescence in situ hybridization result was negative. Targeted next-generation sequencing (NGS) revealed mutations in the TNFRSF14, CREBBP, STAT6, BCL6, CD79B, CD79A, and KLHL6 genes, without evidence of BCL2 or BCL6 rearrangement. The pathologic and genetic features were consistent with t(14;18)-negative FL. Two months after one cycle of bendamustine and rituximab chemotherapy, the patient developed left flank pain. Positron emission tomography/CT showed new development of a large hypermetabolic mass in the retroperitoneum. Needle biopsy of the retroperitoneal mass demonstrated diffuse proliferation of large plasmablastic cells, which were negative for the B-cell markers, BCL2, BCL6, and CD10; they were positive for MUM-1, CD138, CD38, and C-MYC. The pathologic findings were consistent with PBL. The clonal relationship between the initial FL and subsequent PBL was analyzed via targeted NGS. The tumors shared the same CREBBP, STAT6, BCL6, and CD79B mutations, strongly suggesting that the PBL had transformed from a FL clone. The PBL also harbored BRAF V600E mutation and IGH::MYC fusion in addition to IGH::IRF4 fusion.ConclusionsWe propose that transformation or divergent clonal evolution of FL into PBL can occur when relevant genetic mutations are present. This study broadens the spectrum of histological transformation of t(14;18)-negative FL and emphasizes its biological and clinical heterogeneity.

Memory CD8 T cells are vulnerable to chronic IFN-γ signals but not to CD4 T cell deficiency in MHCII-deficient mice

The mechanisms by which the number of memory CD8 T cells is stably maintained remains incompletely understood. It has been postulated that maintaining them requires help from CD4 T cells, because adoptively transferred memory CD8 T cells persist poorly in MHC class II (MHCII)-deficient mice. Here we show that chronic interferon-γ signals, not CD4 T cell-deficiency, are responsible for their attrition in MHCII-deficient environments. Excess IFN-γ is produced primarily by endogenous colonic CD8 T cells in MHCII-deficient mice. IFN-γ neutralization restores the number of memory CD8 T cells in MHCII-deficient mice, whereas repeated IFN-γ administration or transduction of a gain-of-function STAT1 mutant reduces their number in wild-type mice. CD127high memory cells proliferate actively in response to IFN-γ signals, but are more susceptible to attrition than CD127low terminally differentiated effector memory cells. Furthermore, single-cell RNA-sequencing of memory CD8 T cells reveals proliferating cells that resemble short-lived, terminal effector cells and documents global downregulation of gene signatures of long-lived memory cells in MHCII-deficient environments. We propose that chronic IFN-γ signals deplete memory CD8 T cells by compromising their long-term survival and by diverting self-renewing CD127high cells toward terminal differentiation.

Integrated Clinical Genotype-Phenotype Characteristics of STAT3-Mutated Myeloid Neoplasms.

STAT3 is a key transcription factor that mediates cancer progression through phosphorylation or gain-of-function mutations. STAT3 activation in myeloid neoplasms (MN) is primarily mediated through phosphorylation. STAT3 mutation has only rarely been reported in MNs. We assessed the clinicopathologic and molecular genetic features of 32 STAT3-mutated MNs. The frequency of STAT3 mutation in MNs was <0.5%. Twenty (62.5%) cases were classified as acute myeloid leukemia, 7 (21.9%) as myelodysplastic syndrome, and 5 (15.6%) as chronic myelomonocytic leukemia, but none as myeloproliferative neoplasms. STAT3 mutations occurred at initial diagnosis in 22 (88%) cases or at relapse or upon leukemic transformation. Clonal hierarchy analysis revealed that STAT3 mutations represented the dominant clone in 30% of acute myeloid leukemia cases but were subclonal in myelodysplastic syndrome and chronic myelomonocytic leukemia. Most were missense mutations located at the SH2 domain, Y640F being the most common. STAT3 mutation was accompanied by coexisting mutations in all cases, most frequently SRSF2, TET2, ASXL1, and SETBP1. STAT3 mutations were usually associated with morphologic dysplasia, increased blasts, and monosomy 7/del7q. With a median follow-up of 24.5 months, 21 patients died, 6 had persistent disease, and 5 achieved complete remission after stem cell transplantation. STAT3 mutation is present in various MNs but not in myeloproliferative neoplasms. It is often an early event or occurs upon leukemic transformation, which suggests an important role in the pathogenesis and progression of MNs by activating the JAK-STAT pathway. It may help determine a subset of patients with MNs who may benefit from targeted therapy. See related commentary by Hochman and Frank, p. 4554.

Sintilimab (anti-PD-1 antibody) plus chidamide (histone deacetylase inhibitor) in relapsed or refractory extranodal natural killer T-cell lymphoma (SCENT): a phase Ib/II study.

Anti-PD-1 antibodies are a favorable treatment for relapsed or refractory extranodal natural killer T cell lymphoma (RR-ENKTL), however, the complete response (CR) rate and the duration of response (DOR) need to be improved. This phase 1b/2 study investigated the safety and efficacy of sintilimab, a fully human anti-PD-1 antibody, plus chidamide, an oral subtype-selective histone deacetylase inhibitor in 38 patients with RR-ENKTL. Expected objective response rate (ORR) of combination treatment was 80%. Patients received escalating doses of chidamide, administered concomitantly with fixed-dose sintilimab in 21-days cycles up to 12 months. No dose-limiting events were observed, RP2D of chidamide was 30 mg twice a week. Twenty-nine patients were enrolled in phase 2. In the intention-to-treat population (n = 37), overall response rate was 59.5% with a complete remission rate of 48.6%. The median DOR, progression-free survival (PFS), and overall survival (OS) were 25.3, 23.2, and 32.9 months, respectively. The most common grade 3 or higher treatment-emergent adverse events (AEs) were neutropenia (28.9%) and thrombocytopenia (10.5%), immune-related AEs were reported in 18 (47.3%) patients. Exploratory biomarker assessment suggested that a combination of dynamic plasma ctDNA and EBV-DNA played a vital prognostic role. STAT3 mutation shows an unfavorable prognosis. Although outcome of anticipate ORR was not achieved, sintilimab plus chidamide was shown to have a manageable safety profile and yielded encouraging CR rate and DOR in RR-ENKTL for the first time. It is a promising therapeutic option for this population.

Qualitative Immunoglobulin Deficiency Causes Bacterial Infections in Patients with STAT1 Gain-of-Function Mutations.

STAT1 is a transduction and transcriptional regulator that functions within the classical JAK/STAT pathway. In addition to chronic mucocutaneous candidiasis, bacterial infections are a common occurrence in patients with STAT1 gain-of-function (GOF) mutations. These patients often exhibit skewing of B cell subsets; however, the impact of STAT1-GOF mutations on B cell-mediated humoral immunity remains largely unexplored. It is also unclear whether these patients with IgG within normal range require regular intravenous immunoglobulin (IVIG) therapy. Eleven patients (harboring nine different STAT1-GOF mutations) were enrolled. Reporter assays and immunoblot analyses were performed to confirm STAT1 mutations. Flow cytometry, deep sequencing, ELISA, and ELISpot were conducted to assess the impact of STAT1-GOF on humoral immunity. All patients exhibited increased levels of phospho-STAT1 and total STAT1 protein, with two patients carrying novel mutations. In vitro assays showed that these two novel mutations were GOF mutations. Three patients with normal total IgG levels received regular IVIG infusions, resulting in effective control of bacterial infections. Four cases showed impaired affinity and specificity of pertussis toxin-specific antibodies, accompanied by reduced generation of class-switched memory B cells. Patients also had a disrupted immunoglobulin heavy chain (IGH) repertoire, coupled with a marked reduction in the somatic hypermutation frequency of switched Ig transcripts. STAT1-GOF mutations disrupt B cell compartments and skew IGH characteristics, resulting in impaired affinity and antigen-specificity of antibodies and recurrent bacterial infections. Regular IVIG therapy can control these infections in patients, even those with normal total IgG levels.

DOCK8 and STAT3 cooperate to restrain IgE-inducing T follicular helper cells.

Abstract DOCK8 deficient patients have elevated food specific IgE and severe food allergy. In Dock8-/- mice, we showed that T cell intrinsic DOCK8 restrains the development of IL-13 expressing T follicular helper (Tfh13) cells that drive anaphylactic IgE production. Oral exposure to food results in tolerance, yet T cell intrinsic loss of DOCK8 (T-Dock8-/-) is sufficient to drive Tfh13 differentiation and peanut specific IgE. How DOCK8 prevents Tfh13 differentiation is unknown. In human T cells, DOCK8 promotes STAT3 phosphorylation, an inhibitor of GATA3. We show that mouse DOCK8 promotes STAT3 activity in T cells and STAT3-/- T cells differentiate into Tfh13-like cells in vitro. Yet, T cell specific loss of STAT3 (T-Stat3-/-) did not drive peanut specific IgE or Tfh13 differentiation in vivo after oral peanut. STAT3 patients have high IgE, but not severe food allergies and we found elevated levels of Tfh13s in donors with DOCK8 but not STAT3 mutations, suggesting additional mechanisms to inhibit Tfh13 differentiation. DOCK8 promotes Tregs and we show that the analogous regulatory population for Tfh cells, T follicular regulatory (Tfr) cells were reduced in T-Dock8-/- but not T-Stat3-/- mice. To overcome tolerance, we used oral peanut with cholera toxin; levels of Tfh13s and peanut specific IgE where higher in T-Stat3-/- mice than controls. We propose that DOCK8 and STAT3 cooperate in CD4+ T cells to prevent Tfh13 differentiation.

STAT1 Mutations in Chronic Mucocutaneous Candidiasis Diagnosed in an Adult.

A 30-year-old man presented with oral candidiasis and a history of lung abscess. He experienced recurring oral and skin candidiasis in childhood but spent long periods without any infections. Therefore, immunodeficiency was suspected. T and B lymphocyte and natural killer cell counts as well as immunoglobulin levels were normal. Human immunodeficiency virus test results were negative. Therefore, we suspected chronic mucocutaneous candidiasis (CMC). The signal transducer and activator of transcription (STAT) mutation, the leading cause of CMC, was detected by exome sequencing. Most cases of STAT1 mutations are diagnosed in childhood, but a few are diagnosed in adulthood because Candida infections may not be severe.

Case report: Mutation evolution in a patient with TdT positive high grade B cell lymphoma with MYC and BCL2 rearrangements following the treatment of concurrent follicular lymphoma and diffuse large B-cell lymphoma

BackgroundConcurrent follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL)was reported in some studies, while the diagnosis of TdT (terminal deoxynucleotydil transferase) positive high grade B cell lymphoma (HGBL) with MYC and BCL2 rearrangements (“double hit”) transformed from FL/DLBCL has been rarely reported. Herein, we described the clinical features and mutation profiles of a case diagnosed with TdT positive “double hit” HGBL following the treatment of FL/DLBCL.Case presentationThis is a 43-year-old Chinese man who was diagnosed with low grade FL (account for 80%) combined with DLBCL (20%) at a stage of IVB. The patient presented with BCL2/IGH translocation without MYC rearrangement, as well as the expressions of CD20, CD19, CD10 and BCL2 at the initial diagnosis of FL/DLBCL. MYC rearrangement and TdT expression occurred after the treatment. The targeted sequencing revealed mutations in KMT2D, FOXO1, CREBBP, ATM, STAT6, BCL7A, DDX3X, MUC4, FGFR3, ARID5B, DDX11 and PRKCSH genes were the co-mutations shared by the FL/DLBCL and TdT positive “double hit” HGBL, while CCND3, BIRC6, ROBO1 and CHEK2 mutations specifically occurred after the treatment. The overall survival time was 37.8 and 17.8 months after the initial diagnosis of FL/DLBCL and TdT positive “double hit” HGBL, respectively.ConclusionThis study reports a rare case of TdT positive “double hit” HGBL following the treatment of concurrent FL/DLBCL and highlights the mutation characteristics. Collectively, this study will help enrich the knowledge of TdT positive “double hit” HGBL transformed from FL/DLBCL.

148 Disseminated Histoplasmosis in an Adult with STAT1 Mutation

148 Disseminated Histoplasmosis in an Adult with STAT1 Mutation

Threonine phosphorylation of STAT1 restricts interferon signaling and promotes innate inflammatory responses

Since its discovery over three decades ago, signal transducer and activator of transcription 1 (STAT1) has been extensively studied as a central mediator for interferons (IFNs) signaling and antiviral defense. Here, using genetic and biochemical assays, we unveil Thr748 as a conserved IFN-independent phosphorylation switch in Stat1, which restricts IFN signaling and promotes innate inflammatory responses following the recognition of the bacterial-derived toxin lipopolysaccharide (LPS). Genetically engineered mice expressing phospho-deficient threonine748-to-alanine (T748A) mutant Stat1 are resistant to LPS-induced lethality. Of note, T748A mice exhibited undisturbed IFN signaling, as well as total expression of Stat1. Further, the T748A point mutation of Stat1 recapitulates the safeguard effect of the genetic ablation of Stat1 following LPS-induced lethality, indicating that the Thr748 phosphorylation contributes inflammatory functionalities of Stat1. Mechanistically, LPS-induced Toll-like receptor 4 endocytosis activates a cell-intrinsic IκB kinase-mediated Thr748 phosphorylation of Stat1, which promotes macrophage inflammatory response while restricting the IFN and anti-inflammatory responses. Depletion of macrophages restores the sensitivity of the T748A mice to LPS-induced lethality. Together, our study indicates a phosphorylation-dependent modular functionality of Stat1 in innate immune responses: IFN phospho-tyrosine dependent and inflammatory phospho-threonine dependent. Better understanding of the Thr748 phosphorylation of Stat1 may uncover advanced pharmacologically targetable molecules and offer better treatment modalities for sepsis, a disease that claims millions of lives annually.