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

为了研究LAIR-1在体内的功能，我们在B6背景下培育了LAIR-1 -/-小鼠。淋巴器官表型分析显示LAIR-1 +/+和LAIR-1 -/-动物间差异不大。我们观察到LAIR-1 -/-小鼠脾脏B细胞百分比略有增加，同时T细胞减少，主要是因为CD8 T细胞减少。这可能不是T淋巴细胞异常运输的结果，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，同时NKG2D表达增加。体外实验表明，载有OT-II卵肽的APC培养后，OT-II LAIR-1-/- CD4 T细胞增殖能力低于OT-II LAIR-1+/+ CD4 T细胞。为了研究体内的免疫反应，我们用TNP-OVA免疫动物，发现LAIR-1 -/-小鼠的类转换受到影响。这些动物产生较低水平的特异性IgG2a和IgG2b，而转向IgG1不受影响。通过使用T细胞特异性LAIR-1 -/-动物（CD4 Cre LAIR-1flox/flox），我们证实了类转换缺陷是T细胞特异性的。除此之外，其他初步结果表明，在化学性腹膜炎模型中，LAIR-1 -/-小鼠腹膜中巨噬细胞和嗜酸性粒细胞的募集发生了显著变化，这表明LAIR-1在这些细胞类型向炎症部位的运输中发挥了作用。

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 is probably not the 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 specific 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. In addition to that, 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.