An immunoglobulin heavy-chain gene is altered in two T-cell clones.

Thymus-derived lymphocytes (T cells) show a high degree of discrimination in their responses to various antigens, very similar to the specificity repertoire of antibody-producing B cells. The nature of the T-cell receptor which mediates antigen recognition is obscure, but the ability to discriminate between antigenic specificities implies a range of receptor specificities. Many serological and genetic data suggest that T-cell receptors use the immunoglobulin heavy (H)-chain variable (V) region genes but do not carry the antigenic determinants of the immunoglobulin H-chain constant (C) regions; they also do not seem to carry conventional light (L)-chain V- or C-region determinants. In B cells and derivatives the expression of immunoglobulin genes is manifested, at the DNA level, by an alteration of the restriction enzyme patterns of both the H and L immunoglobulin genes. Specifically, V-gene integration involves joining of a V gene with a J segment (in the case of the H chain probably through an intermediate D segment) so that sites for restriction enzymes will undergo changes in cells in which V-J joining has occurred. Here, we describe Southern filter hybridization experiments using C mu and C kappa probes on the DNA of individual T-cell clones from mice, and present evidence for alteration of sequences adjacent to the C mu gene in the cells.