Monoclonal antibodies against two separate alloantigenic sites of HLA-B40

Two monoclonal antibodies (MB40.2 and MB40.3) which are highly specific for HLA-B40 and HLA-B7 were made. They appear to be directed against two separate alloantigenic sites of these HLA molecules. Semiquantitative analysis of the kinetics of antibody binding show that MB40.2 recognizes a site which shows a degree of cross-reactivity with B7 and is specific to some B40 molecules. This antibody also distinguishes between different molecules types as B40. In contrast, MB40.3 recognizes an antigenic determinant which is less variable between B7 and B40 and more closely approximates a public antigen or common antigenic site. This study suggests that the introduction of monoclonal antibodies into MHC serology not only permits but demands a quantitative analysis of these complex systems of homologous but highly polymorphic molecules.