Functional roles of human class II antigens in T cell proliferative response. Comparison of the DR and DQ molecules using mouse monoclonal antibodies.

The monoclonal antibody (mAb) NC1 recognizing a monomorphic DR determinant and the anti-DQ mAbs PLM2, PLM9, and PLM12 recognizing polymorphic DQ determinants were produced. NC1 reacted with the H1L1 (DR) and H1L2(DRw52, DRw53 and allelic products) complexes of a DR family, while the specificity of PLM12 was DQw3 (previously called TB21). Both PLM2 and PLM9 reacted with the allodeterminant of TA10 (a subtype of DQw3). These three mAbs immunoprecipitated the same H2L3 complex of a DQ family. With the aid of these mAbs, DR molecules but not DQw3 molecules were detected on monocytes in significant quantities. The functional roles of these class II molecules in the T cell proliferative responses to three soluble antigens (PPD, mite, Candida) and alloantigens were examined by blocking assays in vitro. NC1 almost completely inhibited T cell proliferative responses against both soluble antigens and allogeneic antigens. In contrast, PLM2, PLM9 and PLM12 showed no significant inhibitory effects at all. These results indicate that DR and DQ antigens are different in their functional roles as well as their serological and immunochemical characteristics and tissue distributions; these three soluble antigens and the alloantigen were presented in association with determinants residing predominantly on two forms of NC1-reactive molecule, namely the H1L1 and/or H1L2 complex of a DR family but not in association with the DQw3 allodeterminant on the H2L3 complex of a DQ family.