Xu J, Ling E A
Department of Anatomy, Faculty of Medicine, National University of Singapore, Kent Ridge.
J Anat. 1994 Apr;184 ( Pt 2)(Pt 2):285-96.
The effects of bacterial lipopolysaccharide (LPS) on the expression of surface antigens including major histocompatibility complex (MHC) and complement type 3 (CR3) receptors on microglial cells in the corpus callosum in postnatal rat brain were investigated. When LPS was injected intravenously (i.v.) in 1-d-old rats, the immunostaining of callosal amoeboid microglial cells with OX-18 directed against MHC class I antigen was enhanced 24 h after the injection in comparison with the controls. The expression of MHC class II (Ia) antigen on the same cell type as shown by its immunoreactivity with OX-6 was also elicited especially after 2 intraperitoneal (i.p.) injections of LPS. Thus 7 d after a single i.p. injection of LPS into 1-d-old rats, only a few OX-6 positive cells showing a moderate staining reaction were observed in the corpus callosum. The immunoreactivity diminished 14 d after the injection. However, in rats receiving 2 successive i.p. injections of LPS at 1 and 4 d of age and killed 7 d after the 1st injection, a significant number of intensely stained OX-6 positive amoeboid microglial cells were observed in the corpus callosum. The expression of MHC class II antigens induced by 2 injections of LPS was sustained at least until d 14 when the callosal ramified microglial cells, known to be derived from gradual metamorphic transformation of amoeboid microglia, still exhibited intense immunoreactivity with OX-6. The effect of LPS on the expression of CR3 on amoeboid microglial cells was not obvious after a single injection, but the immunoreactivity with OX-42 was also augmented in rats given 2 i.p. administration of LPS into rats at 1 an 4 d of age. It is concluded from this study that the expression of MHC class I and class II antigens on amoeboid microglial cells in corpus callosum was upregulated and induced respectively after i.v. or i.p. injection of LPS into early postnatal rats. Although relatively fewer in number when compared with OX-18 and OX-42 positive cells, it is suggested that the OX-6 positive cells would have the potentiality to function in antigen presentation in the postnatal rat brain when challenged by the endotoxin.
研究了细菌脂多糖（LPS）对新生大鼠脑胼胝体小胶质细胞表面抗原表达的影响，这些表面抗原包括主要组织相容性复合体（MHC）和补体3型（CR3）受体。当给1日龄大鼠静脉注射（i.v.）LPS时，与对照组相比，注射后24小时，用针对MHC I类抗原的OX-18对胼胝体阿米巴样小胶质细胞进行免疫染色增强。通过与OX-6的免疫反应性所示，在同一细胞类型上MHC II类（Ia）抗原的表达也被诱导，特别是在2次腹腔注射（i.p.）LPS后。因此，在给1日龄大鼠单次腹腔注射LPS后7天，在胼胝体中仅观察到少数显示中度染色反应的OX-6阳性细胞。注射后14天免疫反应性减弱。然而，在1日龄和4日龄时接受2次连续腹腔注射LPS且在第一次注射后7天处死的大鼠中，在胼胝体中观察到大量强烈染色的OX-6阳性阿米巴样小胶质细胞。2次注射LPS诱导的MHC II类抗原的表达至少持续到第14天，此时已知由阿米巴样小胶质细胞逐渐变形转化而来的胼胝体分支小胶质细胞仍表现出与OX-6的强烈免疫反应性。单次注射后，LPS对阿米巴样小胶质细胞上CR3表达的影响不明显，但在1日龄和4日龄时给大鼠2次腹腔注射LPS的大鼠中，与OX-42的免疫反应性也增强。从这项研究得出的结论是，在新生大鼠早期静脉或腹腔注射LPS后，胼胝体中阿米巴样小胶质细胞上MHC I类和II类抗原的表达分别上调和诱导。尽管与OX-18和OX-42阳性细胞相比数量相对较少，但提示当受到内毒素攻击时，OX-6阳性细胞在新生大鼠脑中具有抗原呈递的潜能。
