RESUMO
Human lymphomedullary tissue cells, separated on the basis of density, Fc and E receptors, show characteristic and consistent differences in their expression of class II MHC antigens. A low density, FcR-ve cell type displays high expression of HLA-DR and acts as the most efficient accessory cell in the induction of a Con A driven proliferative response. Exposure of cells to Con A inhibits subsequent binding of anti-HLA-DR antibodies. Addition of -methyl-D-mannoside reverses both the proliferative response to Con A and returns binding of anti-class II MHC antibodies to normal levels. This experimental system can be used to study: the nature of the association between cell bound molecules and class II MHC products, both spatially and functionally; and the relative functional importance of these products in antigen presentation.