The definition of an MB related specificity by a monoclonal antibody.

A number of monoclonal antibodies have been described that react with monomorphic and polymorphic Ia-like specificities on human B cells, but it is not clear whether these react with HLA-DR encoded molecules or with the products of other closely linked genes within the MHC, such as MB, MT, or DC 1 antigens. A monoclonal antibody is described herein (MC-26.1) which detects a new Ia-like specificity as shown by B-cell reactivity, chemistry, family studies, including recombinant family and coprecipitation studies. The latter studies showed that specificity detected by the MC-26.1 antibody coprecipitated with determinants detected by conventional anti-MB3 and MT3, but not with HLA-DR4 antisera. The determinant was polymorphic but not related to any of the known MB or MT specificities. However, cross-reactions were demonstrated by the variability of reaction on different individuals. Coprecipitation studies indicate that the antigen defined by MC-26.1 coprecipitates with MB and MT specificities suggesting that the antibody defines a new specificity on the MB3 and MT3 molecules.