A monokine which binds to class II histocompatibility proteins

Abstract

SummaryThere is a marked decrease in the viability, in vitro, of dense, immature rat thymocytes over a 4 h incubation period. The addition of a monokine of relative molecular weight 36 000 derived from cultured rat peritoneal macrophages which had been previously stimulated with lipopolysacchandc prevented these cells from dying. The early release of this factor, together with preliminary results of its physical and functional properties suggest that it is distinct from the well characterized monokmes. The macrophage factor was found to bind in competition with a monoclonal antibody directed against a common determinant on the la antigen complex, but also to bind non-competitively with a monoclonal antibody to a strain-specific epitope on la. Based on the results of experiments using a fractionated thymic cell model, it would appear that this monokine binds to the la protein complex on the cell surface of thymic epithelial cells, causing them in turn to release an activity which is responsible for the sur\'i val of thymocytes.