A new determinant, Qa-m208, detected on T lymphocytes and transfected L cells by a Kb-specific monoclonal antibody.

A Kb-specific monoclonal antibody, 6.3.4, defining a new class I specificity, m208, reacts with some K and D region products and with a Qa determinant present on T lymphocytes but not detectable on thymocytes and B lymphocytes. The strain distribution of reactions indicates that this determinant is controlled by the Qa-Tla region, and shows no concordance with the strain distribution pattern of any of the known Qa antigens. The antibody reacts also with L cells expressing a cloned H-2b class I gene mapping in the Qa-Tla region.