Shunyou Gong

Regulation of NKT cell development by SAP, the protein defective in XLP

The adaptor molecule SAP is expressed in T lymphocytes and natural killer (NK) cells, where it regulates cytokine production and cytotoxicity. Here, we show that SAP, encoded by the SH2D1A gene locus, also has a crucial role during the development of NKT cells, a lymphocyte subset with immunoregulatory functions in response to infection, cancer and autoimmune disease. Following stimulation with the NKT cell–specific agonist α-galactosyl ceramide (αGC), Sh2d1a−/− splenocytes did not produce cytokines or activate other lymphoid lineages in an NKT cell–dependent manner. While evaluating the abnormalities in αGC-induced immune responses, we observed that Sh2d1a−/− animals lacked NKT cells in the thymus and peripheral organs. The defect in NKT cell ontogeny was hematopoietic cell autonomous and could be rescued by reconstitution of SAP expression within Sh2d1a−/− bone marrow cells. Seventeen individuals with X-linked lymphoproliferative disease (XLP), who harbored germline mutations in SH2D1A, also lacked NKT cells. Furthermore, a female XLP carrier showed completely skewed X chromosome inactivation within NKT cells, but not T or B cells. Thus, SAP is a crucial regulator of NKT cell ontogeny in humans and in mice. The absence of NKT cells may contribute to the phenotypes of SAP deficiency, including abnormal antiviral and antitumor immunity and hypogammaglobulinemia.

TIPE2, a Negative Regulator of Innate and Adaptive Immunity that Maintains Immune Homeostasis

Immune homeostasis is essential for the normal functioning of the immune system, and its breakdown leads to fatal inflammatory diseases. We report here the identification of a member of the tumor necrosis factor-alpha-induced protein-8 (TNFAIP8) family, designated TIPE2, that is required for maintaining immune homeostasis. TIPE2 is preferentially expressed in lymphoid tissues, and its deletion in mice leads to multiorgan inflammation, splenomegaly, and premature death. TIPE2-deficient animals are hypersensitive to septic shock, and TIPE2-deficient cells are hyper-responsive to Toll-like receptor (TLR) and T cell receptor (TCR) activation. Importantly, TIPE2 binds to caspase-8 and inhibits activating protein-1 and nuclear factor-kappaB activation while promoting Fas-induced apoptosis. Inhibiting caspase-8 significantly blocks the hyper-responsiveness of TIPE2-deficient cells. These results establish that TIPE2 is an essential negative regulator of TLR and TCR function, and its selective expression in the immune system prevents hyperresponsiveness and maintains immune homeostasis.

The mer receptor tyrosine kinase: expression and function suggest a role in innate immunity

The mer receptor tyrosine kinase mediates phagocytosis of apoptotic cells and modulates cytokine production; it is also required for prevention of systemic autoimmune disease. Using a mer‐specific antibody, we have confirmed the presence of mer on macrophages and now report its expression on NK cells, NKT cells, and dendritic cells (DC). We found that DC do not require mer for ingestion of apoptotic cells, as DC from mer‐deficient mice phagocytose apoptotic cells normally. Mer was observed in splenic sections on cells outside follicular areas, probably representing DC and macrophages. Mer apparentlyparticipates in NKT‐cell antigen‐induced signaling, as NKT cells from mer‐deficient mice evinced much lower cytokine production after in vivo α‐galactosylceramide stimulation; this defect was intrinsic to the mer‐deficient NKT cells. Taken together, these studies show mer expression on cells of the innate immune system. Mer, through its binding of lipid antigens, may not only mediate ingestion of apoptotic cells, but also signal events in NK cells, NKT cells, and DC.

Crystal structure of TIPE2 provides insights into immune homeostasis

TNFAIP8-like 2 (TIPE2) has an essential role in immune homeostasis, yet the underlying mechanism remains enigmatic. The high-resolution crystal structure of TIPE2 reveals a previously uncharacterized fold that is different from the predicted fold of a death effector domain (DED). Strikingly, TIPE2 contains a large, hydrophobic central cavity that is poised for cofactor binding. These structural features will be important for understanding the functions of TIPE2 and other TNFAIP8 family proteins.

Critical roles of Bim in T cell activation and T cell–mediated autoimmune inflammation in mice

Bim, the B cell lymphoma 2-interacting (Bcl2-interacting) mediator, maintains immunological tolerance by deleting autoreactive lymphocytes through apoptosis. We report here that Bim is also, paradoxically, required for the activation of autoreactive T cells. Deletion of Bim in hematopoietic cells rendered mice resistant to autoimmune encephalomyelitis and diabetes, and Bim-deficient T cells had diminished cytokine production. Upon T cell receptor activation, Bim-deficient T cells exhibited severe defects in both calcium release and dephosphorylation of nuclear factor of activated T cells (NFAT) but maintained normal levels of activation of NF-kappaB and MAPKs. The defective calcium signaling in Bim-deficient T cells was associated with a significant increase in the formation of an inhibitory complex containing Bcl2 and the inositol triphosphate receptor (IP3R). Thus, in addition to mediating the death of autoreactive T cells, Bim also controlled T cell activation through the IP3R/calcium/NFAT pathway. These results indicate that a single protein is used to control both the activation and apoptosis of autoreactive T cells and may explain why Bim-deficient mice do not reject their own organs despite lacking thymic negative selection.

Genome-wide analysis of pediatric-type follicular lymphoma reveals low genetic complexity and recurrent alterations of TNFRSF14 gene

Pediatric-type follicular lymphoma (PTFL) is a variant of follicular lymphoma (FL) with distinctive clinicopathological features. Patients are predominantly young males presenting with localized lymphadenopathy; the tumor shows high-grade cytology and lacks both BCL2 expression and t(14;18) translocation. The genetic alterations involved in the pathogenesis of PTFL are unknown. Therefore, 42 PTFL (40 males and 2 females; mean age, 16 years; range, 5-31) were genetically characterized. For comparison, 11 cases of conventional t(14:18)(-) FL in adults were investigated. Morphologically, PTFL cases had follicular growth pattern without diffuse areas and characteristic immunophenotype. All cases showed monoclonal immunoglobulin (IG) rearrangement. PTFL displays low genomic complexity when compared with t(14;18)(-) FL (mean, 0.77 vs 9 copy number alterations per case; P <001). Both groups presented 1p36 alterations including TNFRSF14, but copy-number neutral loss of heterozygosity (CNN-LOH) of this locus was more frequently observed in PTFL (40% vs 9%; P =075). TNFRSF14 was the most frequently affected gene in PTFL (21 mutations and 2 deletions), identified in 54% of cases, followed by KMT2D mutations in 16%. Other histone-modifying genes were rarely affected. In contrast, t(14;18)(-) FL displayed a mutational profile similar to t(14;18)(+) FL. In 8 PTFL cases (19%), no genetic alterations were identified beyond IG monoclonal rearrangement. The genetic landscape of PTFL suggests that TNFRSF14 mutations accompanied by CNN-LOH of the 1p36 locus in over 70% of mutated cases, as additional selection mechanism, might play a key role in the pathogenesis of this disease. The genetic profiles of PTFL and t(14;18)(-) FL in adults indicate that these are two different disorders.

Differential chemotactic potential of mouse platelet basic protein for thymocyte subsets.

AbstractMouse platelet basic protein (CXCL7/mPBP) was cloned from thymic stromal cells and further identification indicated that it was expressed in thymic monocytes/macrophages (Mo/Mφs). Recombinant mPBP was chemoattractive for target cells of polymorphonuclear leucocytes, peritoneal Mo/Mφs and splenic lymphocytes with distinct potencies. CXCR2 was identified to be a cognate receptor for mPBP. Mouse thymocyte subsets of CD4-CD8- double-negative (DN), CD4+CD8+ double-positive (DP), CD4+CD8- single-positive (CD4SP) and CD4-CD8+ single-positive (CD8SP) expressed cell surface CXCR2 with different positive percentages and expression levels. mPBP was chemoattractive for thymocyte subsets with the potency order DN>DP> CD8SP>CD4SP, consistent with the levels of CXCR2 expressed on the respective cells. Thus, mPBP in thymus is functionally redundant with chemokine CXCL12/ SDF-1. Moreover, our finding that thymic Mo/Mφs can produce mPBP implies that they may have other functions apart from acting as scavengers in thymus.

Epstein-Barr virus–associated inflammatory pseudotumor presenting as a colonic mass☆

Epstein-Barr virus (EBV)-positive inflammatory pseudotumor (IPT) commonly involves spleen and liver and has only rarely been reported in the gastrointestinal (GI) tract. The spindle cells may express myofibroblastic or follicular dendritic cell markers. We report a challenging case of EBV-positive IPT arising in the ascending colon. The lesion was composed of spindle cells positive for smooth muscle actin but negative for all follicular dendritic cell markers tested and was associated with an exuberant lymphoid proliferation containing reactive follicles, abundant plasma cells, and small lymphocytes. We further discuss pitfalls for possible misdiagnosis as ALK-positive inflammatory myofibroblastic tumor, IgG4-related disease, and peripheral T-cell lymphoma. Our case represents the first EBV-positive inflammatory pseudotumor of the GI tract in the Western literature. Awareness of this rare entity in GI tract is essential for correct diagnosis and appropriate patient management.

Microcystic/reticular Schwannoma: morphological features causing diagnostic dilemma on fine-needle aspiration cytology.

Patient: Male, 28 Final Diagnosis: Microcystic/reticular Schwannoma Symptoms: Neck fullness • finger tingling and numbness Medication: — Clinical Procedure: Surgical resection Specialty: Anatomic Pathology Objective: Rare disease Background: Schwannoma is a common, benign, peripheral nerve sheath tumor. Fine-needle aspiration (FNA) has been very useful for diagnosing classic Schwannoma. Recently, a new morphological variant, the so-called microcystic/reticular Schwannoma, has been recognized. Although histological features of microcystic/reticular Schwannoma have been described, there are no available reports on its FNA cytological appearance. Case Report: A 28-year-old male presented with right arm and finger tingling and numbness. Physical examination found a right lower neck mass. He underwent FNA, followed by needle core biopsy. A diagnosis of microcystic/reticular schwannoma was made. In this case report, we focused on the FNA diagnostic features, thoroughly searched the literature, and discussed relevant information for differential diagnosis. Conclusions: Unlike classic Schwannoma, microcystic/reticular variant has unique cytological features which can mimic those of several morphologically similar mass lesions, making the FNA interpretation more challenging. Cytopathologists should be aware of this new variant of Schwannoma when evaluating FNA cytology of mass lesions showing low-grade, paucicellular, and myxoid features.

Genome-wide analysis reveals TNFAIP8L2 as an immune checkpoint regulator of inflammation and metabolism

HIGHLIGHTSTNFAIP8L2 was preferentially expressed in human myeloid cell types.Tnfaip8l2 expression drastically decreased after lipopolysaccharide treatment in macrophages.Tnfaip8l2 deficiency led to heightened gene expression enriched for leukocyte activation and lipid biosynthesis pathways.Tnfaip8l2 negatively regulated mitochondrial respiration in response to lipopolysaccharide.Hyperlipidemia condition upregulated Tnfaip8l2 gene expression in the adipose tissue. ABSTRACT The interplay between inflammation and metabolism is widely recognized, yet the underlying molecular mechanisms remain poorly characterized. Using experimental database mining and genome‐wide gene expression profiling methods, we found that in contrast to other TNFAIP8 family members, TNFAIP8L2 (TIPE2) was preferentially expressed in human myeloid cell types. In addition, Tnfaip8l2 expression drastically decreased in lipopolysaccharide (LPS)‐stimulated macrophages. Consequently, Tnfaip8l2 deficiency led to heightened expression of genes that were enriched for leukocyte activation and lipid biosynthesis pathways. Furthermore, mitochondrial respiration rate was increased in Tnfaip8l2‐deficient macrophages, as measured by Seahorse metabolic analyzer. Taken together, these results indicate that Tnfaip8l2 serves as a “brake” for immunometabolism, which needs to be released for optimized metabolic reprogramming as well as mounting effective inflammatory responses. The unique anti‐inflammatory and metabolic‐modulatory function of TNFAIP8L2 renders it a novel therapeutic target for cardiovascular diseases and cancer.