Divergent Expression of HLA-DC/MB, -DR, and -SB region products on normal and pathological tissues as detected by monoclonal antibodies

A group of eight monoclonal antibodies directed against different monomorphic determinantsof HLA-class II molecules was used to investigate the distribution of HLA-DC/DS/MB, -DR and -SB-like antigens on normal and pathological lymphoid and nonlymphoid tissues of human adult and fetal donors. HLA-MB/DC/DS-like molecules, as defined by the antibody TÜ 22, showed the most limited distribution as they were detected on B-lymphocytes, monocyte/macrophage subpopulations and distinct interstitial cells of various orpns. HLA-DR and -SB-like antigens characterized by the other anti-HLA-class II reagents (TÜ34, TÜ35, TÜ37, TÜ39, TÜ43, TÜ58) were also present on these cell types. However, selective expression of HLA-DR and/or -SB like molecules was demonstrated with these antibodies on certain vascular endothelia, as well as different B-cell lymphomas and distinct epithelial cells in adults. Exclusive reactivity of the antibody TÜ39 shown on endothelial cells of fetal liver and kidney suggested specific functions of HLA-SB antigens during ontogeny. Furthermore, HLA-DR and/or -SB like molecules but not TÜ22⁺ HLA-DC/MB antigens were found to be inducible on normally Ia-like antigen negative epithelial cells of various diseased organs. Implications of this differential tissue distribution of HLA-DC/MB/DS, -DR and -SB like products in relation to organ transplantation, regulation of immune responses and cell differentiation are discussed.