Immune suppression in vivo with antigen-modified syngeneic cells. V. Interacting T cell subpopulations in the suppressor pathway.

Intravenous administration of syngeneic C57BL/6 cells coupled with the palmitoyl derivative of the protein antigen fowl gamma-globulin (p-FgG) results in a state of FgG carrier-specific nonresponsiveness, mediated in part by suppressor T cells. At least two populations of cells are involved in generating a suppressor pathway in this system, one induced in recipients of p-FgG coupled cells and the other contributed by normal recipients of cells from suppressed donors. Induction of T cells capable of transferring suppression to normal recipients is sensitive to 1) low doses of cyclophosphamide, 2) adult thymectomy, and 3) in vivo treatment with anti-I-J antisera. This T cell subset bears I-J determinants and is functionally sensitive to irradiation. The induction of the second population required for immune suppression is sensitive to 1) low doses of cyclophosphamide and 2) adult thymectomy. In addition, compatibility of genes at the Igh locus appears not to be essential for cellular interaction between these populations. The evidence that interacting T cell subpopulations are involved in a suppressor pathway induced with protein-modified syngeneic cells is discussed relative to other systems in which T-T cell interactions are postulated.