Increased Ia expression, T lymphocyte subset abnormalities and autoimmunity in murine strains bearing the lpr gene.

Defects in cellular communication are fundamental to the development of autoimmune disease. Modulation of immunoregulatory events can be mediated by cellular expression of Ia antigens. We have analysed, by flow cytometry, the Ia antigenic levels on cells from mice expressing the lpr gene and their congenic counterparts. Surface Ia expression is dramatically increased on bone marrow, thymus, lymph node and spleen cells from lpr mice even prior to characteristic lymph node and spleen enlargement. In addition, IL-2 production abnormalities occur in the low density Lyt 1 subset of Thy 1.2 positive cells of normal mice which may be the counterpart of the majority cell type of lpr lymphocytes. Treatment of lpr mice with low dose whole body irradiation (300 rad) decreases lymphadenopathy, autoantibodies, proteinuria and the resident Ia positive cell population while increasing survival. We conclude that lymphoid alterations induced by irradiation reflect a recovery of immunological control associated with suppression of autoimmune manifestations.