Some biological properties of beta2-microglobulin and its antibody.

beta2-Microglobulin on the surface of lymphocytes exists in two molecular forms, first as part of the HL-A antigen complex, and second as a free molecule unbound to other membrane macromolecules. Quantitative determinations of the numbers of molecules of beta2-microglobulin per lymphocyte when compared to published values for the numbers of HL-A molecules per cell are consistent with an excess of beta2-microglobulin compared to HL-A antigens on the cell surface. Turnover studies of beta2-microglobulin from the lymphocyte surface indicated that both beta2-microglobulin and HL-A components are metabolized at similar rates. beta2-Microglobulin appears to be released in the free form. HL-A antigens, if released from the cell surface, appear to be released unbound to beta2-microglobulin. The effects of anti-beta2-microglobulin antibody on lymphocyte activation, namely on the mixed lymphocyte reaction and on antigen induced proliferative response, were studied. Anti-beta2-microglobulin completely inhibited the mixed lymphocyte reaction and the antigen induced proliferative response.