PHAGOCYTOSIS OF APOPTOTIC LYMPHOCYTES BY OLIGODENDROCYTES IN EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS

The alterations in oligodendrocytes in myelin basic protein-induced ac ute experimental autoimmune encephalomyelitis (EAE) in the Lewis rat w ere studied using the technique of pre-embedding immunolabeling with t he Rip monoclonal antibody, which specifically labels the cytoplasm of the cell bodies and processes of oligodendrocytes, In spinal cord sec tions of untreated and dexamethasone-treated rats with EAE, we found t hat apoptotic lymphocytes were phagocytosed by Rip-positive oligodendr ocytes as well as by CD11b/c-positive macrophages/microglia and by ast rocytes expressing glial fibrillary acidic protein. Morphologically no rmal lymphocytes were also internalised by these cell types. a phenome non known as emperipolesis. We suggest that this phenomenon represents the phagocytosis of lymphocytes that have undergone the plasma membra ne alterations of apoptosis without yet manifesting the nuclear conden sation of apoptosis. We also found an increase in the number of cluste rs of two to four oligodendrocytes, mainly in rile grey matter, sugges ting proliferation of cells of the oligodendrocyte lineage.