Mouse alloantibodies capable of blocking cytotoxic T cell function. II. Further study on the relationship between the blocking antibodies and the products of the Lyt-2 locus.

The specificity of mouse alloantibodies which blocked allogeneic killer cells has been confirmed as Ly-2.2 using B6 X C3H recombinant inbred (RI) strains. All of the RI strains tested were sensitive to the cell-mediated lymphocytotoxicity (CML)-blocking effect of our C3H anti-B 10.BR antisera and also carried the Lyt-2b allele. This result and studies using Lyt-2-congenic strains firmly localized the genes encoding the target antigen of CML-blocking antibodies in or near the Lyt-2 locus. In addition, a monoclonal anti-Lyt-2.2 antibody was found to block the CML reaction of B6 killer cells, but not that of B6 Ly-2.1 killers. Blocking antibodies to one allele blocked killing by Lyt-2-heterozygous F1 killer cells, but the inhibition curve reached a plateau at a significantly lower level than that seen on the killer cells of the sensitive parent. Our results thus suggest that Lyt-2 antigens are of functional significance on killer T cells, but do not reveal whether or not that significance involves the T cell receptor.