Regulation Of The Immune Response By The Inositol Phosphatase SHIP

为了避免SHIP生殖系缺失的多效性，我们产生了条件基因敲除小鼠，其SHIP基因的缺失仅限于T细胞、B细胞或巨噬细胞。我们相信这些小鼠是解决SHIP在各种免疫细胞中的内在作用的最佳系统。我们的数据显示，SHIP对于调节T细胞的Th1/Th2反应、确定抗体亲和力和B细胞的同型转换以及抑制巨噬细胞的形成(可以限制IL17和其他炎症反应)是必不可少的。通过将这些小鼠的表型与Ship缺失小鼠的表型进行比较，我们已经能够评估髓系失调对淋巴细胞激活状态的影响。 我们发现SHIP缺失小鼠的表型与淋巴细胞限制性缺失SHIP小鼠的表型不一致，表明SHIP缺失小鼠的淋巴细胞活化表型是SHIP缺失小鼠髓系细胞调节失调的次要效应。我们通过对SHIP缺失仅限于巨噬粒细胞谱系的小鼠的分析证实了这一假设。这些小鼠是通过培育由LysMcre启动子37驱动的Cre重组酶表达的SHIP小鼠而产生的。LysMcre Ship条件性小鼠发展出一种骨髓增殖性病理，减少了它们的寿命，尽管疾病的严重性没有SHIP空小鼠那么可怕(Tarasenko和Bolland，未发表)。对于为什么LysMcre缺失Ship不能完全概括在Ship缺失小鼠中观察到的病理，一个可能的解释是LysMcre中Ship的缺失发生在已经分化的巨噬细胞中，而不是在早期的前体细胞中，后者在没有Ship的情况下可能更具致病性。另一种可能的解释是，除巨噬细胞和粒细胞外，其他细胞对SHIP缺失小鼠的整体表型也有贡献。 巨噬细胞中SHIP的缺失不仅会导致髓系细胞的过度增殖，而且还会导致淋巴细胞的激活。LysMcre Ship条件性小鼠发育成脾肿大，有大量激活的淋巴细胞。我们确定这些小鼠中的T细胞偏向Th17表型，并扩大了调节群体(T.Tarasenko和B.Bolland，未发表的数据)。这一结果解释了在SHIP缺失小鼠的T细胞中观察到的表型是由明显的巨噬细胞过度活动引起的，而不是SHIP在T细胞发育中的明显作用。具体地说，我们的数据与以下观点一致：SHIP缺陷的巨噬细胞对生长因子刺激(如脑脊液)高度敏感，并释放炎性细胞因子(IL6等)，促进T细胞IL17偏向。此外，我们观察到LysMcre Ship条件性小鼠缺乏抑制巨噬细胞的类型，据报道，这种类型的巨噬细胞可以保持免疫原性树突状细胞在Check 53中。对这些巨噬细胞SHIP有条件缺失的小鼠的进一步分析将深入了解髓系细胞的自发激活如何影响整个免疫反应并导致慢性炎症病理。

To avoid the pleiotropic effects of the SHIP germline deletion, we have generated conditional knockout mice with deletion of SHIP restricted to T cell, B cells, or macrophages. We believe these mice are the optimal system to address SHIPs intrinsic roles in a variety of immune cells. Our data show that SHIP is essential for the regulation of Th1/Th2 responses by T cells, in determining antibody affinity and isotype switching in B cells, and for the formation of suppressor macrophages that can limit IL17 and other inflammatory responses. By comparing phenotypes of these mice with that of the total SHIP deletion in SHIP-null mice, we have been able to assess the impact that myeloid dysregulation can inflict on the lymphocyte activation status. We have found discordance between the phenotype of SHIP-null mice and that of mice with lymphocyte-restricted deletion of SHIP, indicating that the activated phenotype of lymphocytes in SHIP-null mice occurs as a secondary effect of the dysregulation of SHIP-deficient myeloid cells. We have confirmed this hypothesis by the analysis of mice with SHIP deletion restricted to the macrophagegranulocyte lineage. These mice were generated by breeding SHIP floxed mice to mice with Cre recombinase expression driven by the LysMcre promoter 37. LysMcre SHIP conditional mice develop a myeloproliferative pathology that reduces their lifespan, although the severity of disease is not as dire as in SHIP null mice (Tarasenko and Bolland, unpublished). One possible explanation as to why the LysMcre deletion of SHIP does not completely recapitulate the pathology observed in SHIP-null mice is that the deletion of SHIP in LysMcre occurs in already differentiated macrophages but not in earlier precursors that could be potentially be more pathogenic in the absence of SHIP. Another possible explanation is that cells other than macrophages and granulocytes contribute to the overall phenotype in SHIP-null mice. Deletion of SHIP in macrophages not only leads to myeloid hyperproliferation, but also to lymphocyte activation as a secondary effect. LysMcre SHIP conditional mice develop splenomegaly with a large number of activated lymphocytes. We determined that T cells in these mice are biased toward the Th17 phenotype and expand the regulatory population (T.Tarasenko and B. Bolland, unpublished data). This result explains the phenotype observed in T cells from SHIP-null mice as resulting from overt macrophage hyperactivity as opposed to a clear role for SHIP in T cell development. Specifically, our data is consistent with the view that SHIP-deficient macrophages are hypersensitive to growth factor stimulation (e.g. CSF) and release inflammatory cytokines (IL6 and others) that promote T cell IL17 bias. Additionally, we observed that LysMcre SHIP conditional mice lack the type of suppressor macrophages that has been reported to keep immunogenic dendritic cells in check 53. Further analysis of these mice with conditional deletion of SHIP in macrophages will give insight into how spontaneous activation of myeloid cells can influence the entire immune response and lead to a chronic inflammatory pathology.