Expression of MHC class II CD4+ and ED1 molecules in association with selective hippocampal neuronal degeneration after long-term adrenalectomy

The neuroendocrine and the immune systems are interconnected. Monoclonal antibodies against major histocompatibility complex (MHC) class I, class II, CD4, CD8, pan T cells, and macrophages were used for immunostaining brains from adrenalectomized (ADX) and shamoperated rats to investigate the potential involvement of the immune/inflammatory mechanisms in the neurodegeneration of hippocampus after ADX. Our results demonstrate upregulation of MHC class II, CD4 antigens and activated microglial marker-ED1 expression selectively in the hippocampus after ADX. The absence of CD5 reactivity precludes that these activated cells were T lymphocytes. The activated microglial cells may either be instrumental in the hippocampal neuronal loss or activated secondarily to the neuronal degeneration after long-term adrenalectomy.