Serologic evidence for antigens controlled by the Ir region in mice.

Antibodies produced in B10.D2 mice against soluble lymphocyte membrane antigens of B10.A (H-2(a)) mice reacted only with lymphocytes of the strains carrying the Ir(k) region, i.e., B10.A(2R), B10.K, B10.BR, B10.HTT, AQR, A.TE, C3H, and CBA; they did not react with cells of strains carrying different Ir regions, i.e., B10.A(4R), B10, B10.M, A.SW, DBA/1. It is therefore concluded that the antigen detected with these antibodies is apparently controlled by the Ir region of the H-2 complex. The antigen is present on some T lymphocytes and absent on B lymphocytes. Its presence or absence seems to correlate with MLC and GVH reactivity.