Effects of ANTI-Ia sera on mitogenic responses: III. Mapping the genes controlling the expression of Ia determinants on concanavalin A-reactive cells to the I-J subregion of the H-2 gene complex*

We have shown that the la determinants expressed on nylon wool-purified T lymphocytes reactive to concanavalin A (Con A) in serum-free media are coded in a single I subregion of the H-2 gene complex. This region, I-J, is defined by two pairs of intra-H-2 recombinant haplotypes: H-2^t3, H-2^t4 and H-2^t3, H-2^t5, carried by B10.HTT, B10.S(9R), B10.A(3R), and B10.A(5R), respectively. No activity against Con A-reactive T cells has been detected in any antiserum that was produced in strain combinations which shared a common I-J region. This suggests that la antigens expressed on Con A-reactive T cells are restricted to the I-J subregion.