Antibodies to major histocompatibility complex class II inhibit proliferation, but increase production of soluble CD23 in lymphoblastoid B-cell lines

Class II major histocompatibility complex (MHC) proteins bind and present peptide antigens to T cells. Moreover, their function as signal transduction molecules has recently been emphasized. Here we used Epstein-Barr virus (EBV)-transformed B-cell lines (B-LCL) in experiments to investigate the changes induced by binding of specific antibodies to HLA-DR molecules. Binding of the antibodies induced, in an allele-specific manner, striking non-cytotoxic inhibition of B-LCL proliferation. This inhibition was associated with an increase in shedding of soluble CD23. These findings provide further evidence for the function of MHC class II proteins as signal transduction molecules which may be important in B-cell activation.