Role of LAIR-1 and CD300 Family Receptors in Regulating Inflammation

我们已经在B6背景下产生了LAIR-1 -/-小鼠以研究LAIR-1的体内功能。淋巴器官的表型分析未显示LAIR-1 +/+和LAIR-1 -/-动物之间存在较大差异。我们观察到LAIR-1 -/-小鼠脾B细胞百分比略有增加，沿着T细胞减少，主要是因为CD 8 T细胞减少。这可能不是由T淋巴细胞的异常运输引起的，因为LAIR-1 +/+和LAIR-1 -/- T细胞同样运输到外周淋巴器官。在肠道中，我们观察到LAIR-1 -/-小鼠的T细胞略有增加，沿着NKG 2D表达增加。体外实验表明，当OT-II LAIR-1-/-CD 4 T细胞与负载OT-II OVA肽的APC一起培养时，OT-II LAIR-1-/-CD 4 T细胞的增殖低于OT-II LAIR-1+/+ CD 4 T细胞。为了研究体内免疫应答，我们用TNP-OVA免疫动物，发现LAIR-1 -/-小鼠的类别转换受到影响。这些动物产生较低水平的IgG 2a和IgG 2b，而转换为IgG 1不受影响。通过使用T细胞特异性LAIR-1 -/-动物（CD 4 Cre LAIR-1flox/flox），我们证实了类别转换中的缺陷是T细胞特异性的。先前的研究者已经发表小鼠B细胞不表达LAIR-1;然而，最近我们发现边缘区B细胞对LAIR-1表达呈阳性。其他初步结果表明，在LAIR-1 -/-小鼠中，在化学性腹膜炎模型中，巨噬细胞和嗜酸性粒细胞向腹膜中的募集存在显著改变，表明LAIR-1在这些细胞类型向炎症部位运输中的作用。 我们发现，人外周血中性粒细胞表达CD 300 α。为了研究中性粒细胞发育过程中的表达，我们使用HL-60分化模型。我们发现，CD 300 a表达是在发育过程中获得的，当中性粒细胞用LPS和GM-CSF刺激时，细胞表面表达增加非常迅速。这种增加是受体的细胞内池易位到细胞表面的结果。CD 300 a的这种现成可用性使人想起CTLA-4，并表明CD 300 a在调节中性粒细胞应答中可能发挥重要作用。CD 300 a与含ITAM的CD 32a（FcRIIa）活化受体的共连接抑制CD 32a介导的信号传导，而其不抑制toll样受体（TLR）-4介导的活性氧（ROS）产生。因此，至少对于人中性粒细胞，似乎由CD 300 a受体介导的抑制信号在其作用中可能是选择性的。

We have generated LAIR-1 -/- mice on a B6 background to study the in vivo function of LAIR-1. Phenotypic analysis of lymphoid organs did not show large differences between LAIR-1 +/+ and LAIR-1 -/- animals. We have observed a slight increase in the percentage of splenic B cells in the LAIR-1 -/- mice, along with a decrease in T cells, mostly because of a decrease in CD8 T cells. This probably does not result from abnormal trafficking of T lymphocytes, since LAIR-1 +/+ and LAIR-1 -/- T cells traffic equally to peripheral lymphoid organs. In the gut we have observed a slight increase of T cells in the LAIR-1 -/- mice, along with an increase in the NKG2D expression. In vitro experiments showed that OT-II LAIR-1-/- CD4 T cells proliferated less than the OT-II LAIR-1+/+ CD4 T cells when they are cultured with APC loaded with OT-II OVA peptide. To study the immune response in vivo, we have immunized the animals with TNP-OVA and found that class switching is affected in LAIR-1 -/- mice. These animals produced lower levels of IgG2a and IgG2b, while switching to IgG1 is not affected. By using T cell specific LAIR-1 -/- animals (CD4 Cre LAIR-1flox/flox), we confirmed that the defect in class switching is T cell specific. Previous investigators have published that mouse B cells do not express LAIR-1; however, recently we have found that marginal zone B cells are positive for LAIR-1 expression. Other preliminary results have shown that in the LAIR-1 -/- mice there are significant alterations in the recruitment of macrophages and eosinophils into the peritoneum in a model of chemical peritonitis, suggesting a role for LAIR-1 in the trafficking of these cell types towards sites of inflammation. We showed that human neutrophils from peripheral blood express CD300a. To study expression during neutrophil development, we used the HL-60 differentiation model. We showed that CD300a expression is acquired during development and that cell surface expression increases very rapidly when neutrophils are stimulated with LPS and GM-CSF. This increase is the result of translocation of an intracellular pool of the receptor to the cell surface. This ready availability of CD300a is reminiscent of CTLA-4 and suggests that CD300a could play an important role in modulating neutrophil responses. Co-ligation of CD300a with the ITAM containing CD32a (FcRIIa) activation receptor inhibited CD32a mediated signaling, whereas it did not inhibit toll-like receptor (TLR)-4 mediated reactive oxygen species (ROS) production. Therefore, at least for human neutrophils, it seems that the inhibitory signals mediated by the CD300a receptor may be selective in their action.