Regulation Of The Immune Response By The Inositol Phosphatase SHIP

在SHIP-null小鼠中观察到淋巴细胞异常，但尚不清楚它们是由于这些细胞中SHIP的内在需求还是严重髓系病理的结果。为了精确定位SHIP在T细胞中的功能，我们产生了T细胞特异性缺失SHIP的小鼠。在没有SHIP的情况下，我们发现胸腺选择或周围调节性T细胞的激活状态和数量没有差异。相比之下，ship缺陷T细胞在体外不能有效地向Th2倾斜。T细胞特异性缺失SHIP的小鼠在明矾/NP-CGG免疫后抗体反应较差，在曼氏血吸虫卵刺激下Th2细胞因子产生减少。未能向Th2反应倾斜可能是th1相关转录因子T-bet基础水平升高的结果，这是由于对细胞因子介导的T-bet诱导的敏感性增强所致。ship缺陷CD8+细胞表现出增强的细胞毒性反应，与这些细胞中升高的T-bet水平一致。总的来说，我们的实验表明，在T细胞中，SHIP负调控细胞因子介导的激活，从而允许有效的Th2反应并限制T细胞的细胞毒性。

Lymphocyte anomalies have been observed in SHIP-null mice but it is unclear whether they are due to an intrinsic requirement of SHIP in these cells or a consequence of the severe myeloid pathology. To precisely address the function of SHIP in T cells we have generated mice with T cell-specific deletion of SHIP. In the absence of SHIP, we found no differences in thymic selection or in the activation state and numbers of regulatory T cells in the periphery. In contrast, SHIP-deficient T cells do not skew efficiently to Th2 in vitro. Mice with T cell-specific deletion of SHIP show poor antibody responses upon Alum/NP-CGG immunization and diminished Th2 cytokine production when challenged with Schistosoma mansoni eggs. The failure to skew to Th2 responses may be the consequence of increased basal levels of the Th1-associated transcriptional factor T-bet, resulting from enhanced sensitivity to cytokine-mediated T-bet induction. SHIP-deficient CD8+ cells show enhanced cytotoxic responses, consistent with elevated T-bet levels in these cells. Overall our experiments indicate that in T cells, SHIP negatively regulates cytokine-mediated activation in a way that allows effective Th2 responses and limits T cell cytotoxicity. Aggregation of the high affinity IgE receptor (Fc-epsilon-RI) on mast cells initiates signaling pathways leading to degranulation and cytokine release. It has been reported that SHIP-1 negatively regulates Fc-epsilon-RI-triggered pathways but it is unknown whether its homologous protein SHIP-2 has the same function. We have used a lentiviral based RNA interference technique to obtain SHIP-2 knockdown bone marrow-derived mast cells (BMMCs) and have found that elimination of SHIP-2 results in both increased mast cell degranulation and cytokine (IL-4 and IL-13) gene expression upon Fc-epsilon-RI stimulation. Elimination of SHIP-2 from BMMCs has no effect on Fc epsilon RI-triggered calcium flux, tyrosine phosphorylation of MAPKs or in actin depolymerization following activation. Rather, we observe that absence of SHIP-2 results in increased activation of the small GTPase Rac-1 and in enhanced microtubule polymerization upon Fc-epsilon-RI engagement. Co-immunoprecipitation experiments in rat basophilic leukemia (RBL 2H3) cells show that SHIP-2 interacts with the FcRI -chain, Gab2 and Lyn and that unlike SHIP-1, it does not associate with SHC in mast cells. Our results report a negative regulatory role of SHIP-2 on mast cell activation that is calcium independent and distinct from the regulation by SHIP-1.