The specificity of cellular immune responses in guinea pigs. III. The precision of antigen recognition by T lymphocytes.

T lymphocytes from guinea pigs immunized with 2,4-dinitrophenyl (DNP) derivatives of mycobacteria respond to a variety of DNP conjugates. Preincubation of such cells with a given DNP conjugate under conditions which lead to the inactivation of responding cells causes a loss of the response to that conjugate, but has little effect on the response to DNP coupled to unrelated carriers. Thus, the responses of such cells to a variety of DNP conjugates can best be explained by the presence of a mixture of highly specific cells each responding to a different antigenic dterminant rather than by the presence of T cells with specificity limited to the hapten itself. Furthermore, the activity of T cells from DNP-mycobacteria-primed donors could not be blocked by a variety of nonstimulatory DNP conjugates. This suggests that while such T cells clearly recognize DNP with great precision, the receptor does not contain a very high affinity site for the hapten. A possible model for such a T-cell receptor is discussed.