Two-chain subunit structure of HLA-D antigens.

Both F(ab')2 fragments and intact antibody from rabbit anti-B-cell antisera were shown to specifically block the mixed lymphocyte culture (MLC) reaction. The antisera, which were raised to papain-solubilized spleen cell membrane antigens, appeared to block the stimulator cell and not the responder cell. Specificity of the blocking was shown in that antisera to beta2 microglobulin would not block the MLC-stimulating cell. Membrane antigens from acute lymphocytic leukemia cells were labeled with 125I, solubilized with sodium deoxycholate and immunoprecipitated with either human or rabbit anti-B-cell antisera. Both sources of antisera precipitated polypeptide subunits of 27,000 and 35,000 daltons.