T-CELLS CAN BE ACTIVATED BY PEPTIDES THAT ARE UNRELATED IN SEQUENCE TO THEIR SELECTING PEPTIDE

We tested the ability of CD4(+) T cells, selected in the thymus by rea ction with class II protein bound to a single peptide, to react with t he same class II protein bound to other peptide!;. The T cells reacted with all peptides tested, including one that was quite unlike the sel ecting peptide in T cell receptor binding residues. The receptors on c lass II/peptide-reactive T cells from class II/single peptide mice wer e similar but not identical to some of those from normal animals. Thus , class II bound to a single peptide selects a subset of T cells that is related to that selected by class II bound to many peptides.