Regulation Of The Immune Response By The Inositol Phosphatase SHIP

为了避免SHIP种系缺失的多效性效应，我们已经产生了限制于T细胞、B细胞或巨噬细胞的SHIP缺失的条件性敲除小鼠。我们相信这些小鼠是解决SHIP在各种免疫细胞中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Th 1/Th 2应答，确定B细胞中的抗体亲和力和同种型转换，以及形成可以限制IL 17和其他炎症反应的抑制性巨噬细胞是必不可少的。通过比较这些小鼠的表型与SHIP缺失小鼠中的总SHIP缺失的表型，我们已经能够评估骨髓调节异常对淋巴细胞活化状态的影响。 我们发现SHIP基因敲除小鼠的表型与淋巴细胞限制性SHIP基因缺失小鼠的表型不一致，表明SHIP基因敲除小鼠中淋巴细胞的活化表型是SHIP基因缺陷型骨髓细胞调节异常的继发效应。我们已经证实了这一假设的分析与SHIP基因缺失的小鼠局限于巨噬细胞系。这些小鼠通过将SHIP floxed小鼠与具有由LysMcre启动子37驱动的Cre重组酶表达的小鼠交配而产生。LysMcre SHIP条件性小鼠出现骨髓增生性病理，缩短其寿命，尽管疾病的严重程度不像SHIP无效小鼠那样可怕（Tarasenko和Bolland，未发表）。关于为什么SHIP的LysMcre缺失不能完全重现在SHIP缺失小鼠中观察到的病理学的一种可能的解释是，LysMcre中的SHIP缺失发生在已经分化的巨噬细胞中，而不是发生在早期前体中，所述早期前体在没有SHIP的情况下可能更具致病性。另一种可能的解释是，巨噬细胞和粒细胞以外的细胞有助于SHIP基因敲除小鼠的整体表型。 巨噬细胞中SHIP的缺失不仅导致骨髓过度增殖，还导致淋巴细胞活化作为次级效应。LysMcre SHIP条件小鼠出现脾肿大，伴有大量活化淋巴细胞。我们确定这些小鼠中的T细胞偏向于Th 17表型并扩增调节群体（T.Tarasenko和B. Bolland，未公布的数据）。该结果解释了在来自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跃引起的，而不是SHIP在T细胞发育中的明确作用。具体而言，我们的数据与SHIP缺陷型巨噬细胞对生长因子刺激（例如CSF）超敏并释放促进T细胞IL 17偏向的炎性细胞因子（IL 6和其他）的观点一致。此外，我们观察到LysMcre SHIP条件小鼠缺乏抑制性巨噬细胞的类型，该抑制性巨噬细胞已被报道保持免疫原性树突细胞处于检查状态53。对这些巨噬细胞中SHIP有条件缺失的小鼠的进一步分析将深入了解骨髓细胞的自发活化如何影响整个免疫应答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.