SH2D1A, which encodes signaling lymphocyte activation molecule (SLAM)-associated protein (SAP), is altered in patients with X-linked lymphoproliferative disease (XLP), a primary immunodeficiency. SAP-deficient mice infected with lymphocytic choriomeningitis virus had greatly increased numbers of CD8+ and CD4+ interferon-gamma-producing spleen and liver cells compared to wild-type mice. The immune responses of SAP-deficient mice to infection with Leishmania major together with in vitro studies showed that activated SAP-deficient T cells had an impaired ability to differentiate into T helper 2 cells. The aberrant immune responses in SAP-deficient mice show that SAP controls several distinct key T cell signal transduction pathways, which explains in part the complexity of the XLP phenotypes.

Signaling lymphocyte activation molecule (SLAM), a glycoprotein expressed on activated lymphocytes and antigen-presenting cells, has been shown to be a coregulator of antigen-driven T cell responses and is one of the two receptors for measles virus. Here we show that T cell receptor–induced interleukin (IL)-4 secretion by SLAM−/− CD4+ cells is down-regulated, whereas interferon γ production by CD4+ T cells is only slightly up-regulated. Although SLAM controls production of IL-12, tumor necrosis factor, and nitric oxide in response to lipopolysaccharide (LPS) by macrophages, SLAM does not regulate phagocytosis and responses to peptidoglycan or CpG. Thus, SLAM acts as a coreceptor that regulates signals transduced by the major LPS receptor Toll-like receptor 4 on the surface of mouse macrophages. A defective macrophage function resulted in an inability of SLAM−/− C57Bl/6 mice to remove the parasite Leishmania major. We conclude that the coreceptor SLAM plays a central role at the interface of acquired and innate immune responses.

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The T and natural killer (NK) cell-specific gene SAP (SH2D1A) encodes a 'free SH2 domain' that binds a specific tyrosine motif in the cytoplasmic tail of SLAM (CD150) and related cell surface proteins. Mutations in SH2D1A cause the X-linked lymphoproliferative disease, a primary immunodeficiency. Here we report that a second gene encoding a free SH2 domain, EAT-2, is expressed in macrophages and B lympho cytes. The EAT-2 structure in complex with a phosphotyrosine peptide containing a sequence motif with Tyr281 of the cytoplasmic tail of CD150 is very similar to the structure of SH2D1A complexed with the same peptide. This explains the high affinity of EAT-2 for the pTyr motif in the cytoplasmic tail of CD150 but, unlike SH2D1A, EAT-2 does not bind to non-phosphorylated CD150. EAT-2 binds to the phosphorylated receptors CD84, CD150, CD229 and CD244, and acts as a natural inhibitor, which interferes with the recruitment of the tyrosine phosphatase SHP-2. We conclude that EAT-2 plays a role in controlling signal transduction through at least four receptors expressed on the surface of professional antigen-presenting cells.

More than half of patients with X-linked lympho-proliferative disease, which is caused by a defect in the intracellular adapter protein SH2D1A, suffer from an extreme susceptibility to EpsteinBarr virus. One-third of these patients, however, develop dysgammaglobulenemia without an episode of severe mononucleosis. Here we show that in SH2D1A ؊/؊ mice, both primary and secondary responses of all Ig subclasses are severely impaired in response to specific antigens. Because germinal centers were absent in SH2D1A ؊/؊ mice upon primary immunization, and because SH2D1A was detectable in wt germinal center B cells, we examined whether SH2D1A ؊/؊ B cell functions were impaired. Using the adoptive cotransfer of B lymphocytes from hapten-primed SH2D1A ؊/؊ mice with CD4 ؉ T cells from primed wt mice into irradiated wt mice provided evidence that signal transduction events controlled by SH2D1A are essential for B cell activities resulting in antigen specific IgG production. Defects in naïve SH2D1A ؊/؊ B cells became evident upon cotransfer with nonprimed wt CD4 ؉ cells into Rag2 ؊/؊ recipients. Thus, both defective T and B cells exist in the absence of SH2D1A, which may explain the progressive dysgammaglobulinemia in a subset of X-linked lympho-proliferative disease patients without involvement of Epstein-Barr virus.Epstein-Barr virus ͉ germinal center ͉ immunoglobulin ͉ SLAM͞CD150

Background: Team-based learning (TBL) has become a more commonly recognized and implemented pedagogical approach in curricula of numerous disciplines. The desire to place more autonomy on the student and spend less in-class time delivering content has resulted in complete or partial adoption of this style of learning in many educational settings. Aim: Provide faculty with tools that foster a well facilitated and interactive TBL learning environment. Methods: We examined the published literature in the area of facilitation – specifically in TBL environments, and explored learning theories associated with team learning and our own experiences to create these facilitation tips. Results: We created 12 tips for TBL facilitation designed to assist faculty to achieve an effective and engaging TBL learning environment. Conclusions: Applying these twelve tips while facilitating a TBL classroom session will help to ensure maximal participation and optimal learning in a safe yet stimulating environment.

[SLAM]) is the prototypical member of a growing family of glycoprotein receptors on hematopoietic cells, which includes CD229, CD84, CD244, SF2000/Ly108, SF2001, and 19A(CRACC). [1][2][3][4][5][6][7][8] This "SLAM family" is defined by close sequence homology of the receptors that have one or more cytoplasmic tyrosine motifs with the consensus sequence Thr-(Ile/Val)-pTyr-x-x-Val. [9][10][11] The other members of the family, which do not have cytoplasmic tails (CD48, BCM1-like), are likely to act as ligands, as demonstrated for CD48 that is attached to the membrane by a lipid anchor. The cytoplasmic tyrosine motifs function as docking sites for the small cytoplasmic signaling molecules SLAM-associated protein (SAP, SH2D1A) and EWS/FLI1 activated transcript 2 (EAT). [12][13][14][15] In humans, CD150 is expressed on memory/activated T cells and strongly expressed on T H 1 helper T cells, B cells, thymocytes, and dendritic cells. [16][17][18][19][20][21][22][23][24] CD150 is a self-ligand 25,26 thought to play an important role in adhesion and signaling in the immune synapse between the T cell and antigen-presenting cell (APC). Two major immune functions have been ascribed to CD150 in in vitro human studies, costimulation of T-cell proliferation and augmentation of the interferon ␥ (IFN-␥) response. 18 Many T-cell surface receptors have been shown to function to various degrees as costimulation molecules in that they induce enhanced proliferation during T-cell receptor (TCR) engagement. Examples of these costimulation receptor/ligand pairs include CD28/B7.1/B7.2, ICOS/B7RP1, LFA1/ ICAM, 4-1BB/4-1BBL, OX40/OX40L, and CD27/CD70. 27-32 Unlike the archetypal costimulatory pair CD28/B7, many of these receptor pairs are induced on activation; thus, costimulatory function follows shortly after the initial TCR triggering event.Although CD150 is in this inducible category of receptors, it is different in 2 respects. First, CD150 signals through interaction with SAP in T cells and EAT in APCs. These small (128 amino acids) molecules, which comprise an SH2 domain with a short tail, are structurally similar but differ subtly in their binding characteristics to the SLAM family receptors. 14 Second, CD150 is strongly expressed on the surface of established T H 1 cells and monoclonal antibodies directed at CD150 augment IFN-␥ production following TCR triggering in human T cells. Thus, CD150 has 2 major roles in T-cell activation-costimulation and control of IFN-␥ production.SAP is likely a pivotal signaling molecule for the 6 members of the SLAM family of receptors. This is becoming clear through studies on patients with mutations of the SAP gene sh2d1a, which result in the fatal X-linked lymphoproliferative disease (XLP), familial hemophagocytic lymphohistiocytosis (FHL), and combined variable immunodeficiency (CVID), [33][34][35][36][37] and through studies performed with the SAP Ϫ/Ϫ mouse. 34 For personal use only. on May 12, 2018. by guest www.bloodjournal.org From infectious mononucleosis, B-cell lymphomas, and dysgammaglob...

Cytolytic T cells use two mechanisms to kill virally infected cells, tumor cells, or other potentially autoreactive T cells in short-term in vitro assays. The perforin/granule exocytosis mechanism uses preformed cytolytic granules that are delivered to the target cell to induce apoptosis and eventual lysis. FasL/Fas (CD95 ligand/CD95)–mediated cytolysis requires de novo protein synthesis of FasL by the CTL and the presence of the death receptor Fas on the target cell to induce apoptosis. Using a CD8+ CTL clone that kills via both the perforin/granule exocytosis and FasL/Fas mechanisms, and a clone that kills via the FasL/Fas mechanism only, we have examined the requirement of intra- and extracellular Ca2+ in TCR-triggered cytolytic effector function. These two clones, a panel of Ca2+ antagonists, and agonists were used to determine that a large biphasic increase in intracellular calcium concentration, characterized by release of Ca2+ from intracellular stores followed by a sustained influx of extracellular Ca2+, is required for perforin/granule exocytosis. Only the sustained influx of extracellular Ca2+ is required for FasL induction and killing. Thapsigargin, at low concentrations, induces this small but sustained increase in [Ca2+]i and selectively induces FasL/Fas-mediated cytolysis but not granule exocytosis. These results further define the role of Ca2+ in perforin and FasL/Fas killing and demonstrate that differential Ca2+ signaling can modulate T cell effector functions.