Murine T cell Ia antigens: specificity Iat.46 maps in I-J to I-E chromosomal segment of H-2 complex.

An alloantiserum was prepared in C57BL/10 mice hyperimmunized with concanavalin A-stimulated B10.HTG thymocytes. Absorption with separated B10.A(3R)B and T lymphocytes, followed by titration on these cell types, revealed a new I-region controlled T-cell specificity, Iat.46. The determinant is present on a subpopulation of mature peripheral T cells but not on B lymphocytes, thymocytes, or bone marrow cells. It is also observed using (A.TH X B10.HTT)F1 anti-A.TL antiserum on B10.A(3R) T lymphocytes. The k and d haplotypes are fully crossreactive with regard to Iat.46 expression. B10.HTT, C57BL/10, and BSVS do not carry the Iat.46-encoding allele. Moreover, Iat.46 is not a determinant formed by I-A--I-E gene complementation. The Iat.46-controlling gene, Ia-8, may be positioned to the left of the B10.HTT crossover and to the right of the B10.A(3R) recombinational event. Thus, this determinant may be considered either to represent complexity within the I-J subregion or to demarcate a new I subregion between I-J and I-E.