Williams K C, Dooley N P, Ulvestad E, Waage A, Blain M, Yong V W, Antel J P
Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada.
J Neurosci. 1995 Mar;15(3 Pt 1):1869-78. doi: 10.1523/JNEUROSCI.15-03-01869.1995.
Antigen presentation by endogenous glial cells is postulated to regulate reactivity of immune cells that gain entry into the CNS. We have previously observed, using a mixed lymphocyte reaction (MLR) system, that adult human-derived microglia can function as antigen-presenting cells (APC) for immediately ex vivo CD4+ T cells in a primary MLR (1 degree MLR) whereas astrocytes could not. We have now found that fetal human astrocytes can support CD4+ T cell proliferation in the presence of exogenous human recombinant (r) IL-2, and that astrocytes can support the continued proliferation of CD4+ T cells previously sensitized to sister astrocyte cultures in a secondary MLR. Additionally, adult human microglia, seeded into the nonpriming astrocyte: CD4+ T cell cocultures at non-T cell-stimulatory concentrations of 1000-5000 microglial cells per well, could reverse the inability of astrocytes to present antigen in the primary MLR. To examine the cellular basis for the inability of human astrocytes to function as APCs in the primary MLR, astrocyte- and microglial-enriched populations were established from human embryonic and adult brain, respectively, and analyzed for their ability to synthesize cytokines potentially relevant as accessory signals in the MLR. Microglia had transcript as determined by the reverse transcriptase-polymerase chain reaction (RT-PCR) and protein as determined by bioassay for IL-1 alpha, IL-6, and TNF alpha. Human fetal astrocytes had transcript for IL-6 but not for IL-1 alpha or TNF alpha under basal culture conditions and following IFN gamma stimulation. The addition of human rIL-1 from 1-50 U/ml could reverse the inability of astrocytes to present antigen in the primary MLR. These studies demonstrate that although in vitro highly enriched cultures of astrocytes absent of microglia cannot present antigen to immediately ex vivo blood-derived CD4+ T cells in the MLR, in situ, with the cooperative help of microglia-derived cytokines or accessory surface molecules, astrocytes may function as central nervous system APCs.
内源性神经胶质细胞的抗原呈递被认为可调节进入中枢神经系统的免疫细胞的反应性。我们之前使用混合淋巴细胞反应（MLR）系统观察到，成人来源的小胶质细胞可作为原代MLR（一级MLR）中即时离体CD4 + T细胞的抗原呈递细胞（APC），而星形胶质细胞则不能。我们现在发现，人胎儿星形胶质细胞在存在外源性人重组（r）IL-2的情况下可支持CD4 + T细胞增殖，并且星形胶质细胞可支持先前在二级MLR中对姐妹星形胶质细胞培养物致敏的CD4 + T细胞的持续增殖。此外，以每孔1000 - 5000个小胶质细胞的非T细胞刺激浓度接种到非致敏星形胶质细胞：CD4 + T细胞共培养物中的成人小胶质细胞，可逆转星形胶质细胞在原代MLR中呈递抗原的无能状态。为了研究人星形胶质细胞在原代MLR中不能作为APC发挥作用的细胞基础，分别从人胚胎脑和成人脑中建立了富含星形胶质细胞和小胶质细胞的群体，并分析了它们合成可能与MLR中辅助信号相关的细胞因子的能力。通过逆转录聚合酶链反应（RT-PCR）测定，小胶质细胞有IL-1α、IL-6和TNFα的转录本，通过生物测定法测定有相应蛋白。人胎儿星形胶质细胞在基础培养条件下以及IFNγ刺激后有IL-6的转录本，但没有IL-1α或TNFα的转录本。添加1 - 50 U/ml的人rIL-1可逆转星形胶质细胞在原代MLR中呈递抗原的无能状态。这些研究表明，尽管在体外高度富集的无小胶质细胞的星形胶质细胞培养物不能在MLR中向即时离体的血液来源的CD4 + T细胞呈递抗原，但在原位，在小胶质细胞衍生的细胞因子或辅助表面分子的协同帮助下，星形胶质细胞可能作为中枢神经系统的APC发挥作用。
