Alloreactive T-cell clones. Ly phenotypes predict both function and specificity for major histocompatibility complex products.

We have studied the association of Ly phenotype with function and specificity for major histocompatibility complex (MHC) products by examining the properties of 21 T-cell clones derived from B10 anti-B10.D2 and B10.A anti-B10.D2 mixed lymphocyte cultures (MLC). T cells were selected after MLC solely on the basis of Ly phenotype, cloned by limiting dilution, and tested for stability of Ly phenotype, function and specificity for class I or class II MHC products. Sixteen Ly-1+2- and five Ly-1-2+ T-cell clones were tested. The clones selected for the Ly-1+2- phenotype maintained this phenotype, expressed helper but not lytic function, and recognized class II MHC products (I-Ad or I-Ed). All Ly-1-2+ clones maintained this phenotype, possessed cytolytic but not helper activity, and recognized class I MHC products (Dd and Ld). Our data therefore confirm at the clonal level the original observations of a remarkably consistent correlation between Ly markers, MHC specificity, and function. They suggest that the expression of Ly antigens on T-cell clones forms part of a genetic program for each of these specialized cells that also determines their function and MHC specificity.