Immunohistochemical characterization of the mononuclear cells in the brain of the rat with an experimental chronic Trypanosoma brucei gambiense infection.

The distribution of T-cell subsets, B cells, and class II MHC antigens was examined within the CNS of rats chronically infected with Trypanosoma brucei gambiense, using appropriate mouse monoclonal antibodies. The mononuclear infiltrates of the leptomeninges and the perivascular areas (Virchow-Robin spaces) were composed of IgM-producing plasma cells and Mott cells and T-helper/inducer cells. Cells defined phenotypically as suppressor/cytotoxic T cells were rare. Anti-Ia reactive cells were also abundant in these inflammatory lesions and in the white matter, representing Ia-expressing neuroglial cells, B cells, activated T cells, and macrophages. The Ia-positive neuroglial cells, possibly acting as accessory cells, associated with numerous T-helper/inducer cells and cells from the B-cell lineage, suggest that a T-dependent B-cell immune response can be initiated within the CNS of rats with a chronic T. b. gambiense infection.