Role or I-region gene products in macrophage induction of an antibody response. II. Restriction at the level of T cell in recognition of I-J-subregion macrophage determinants

The effect of specific anti-I-J reagents on macrophage-T cell interactions was studied in an in vitro antibody response to burro erythrocytes. Macrophages were prepared from the spleens of F₁ hybrid mice whose parental strains differed at the I-J subregion. Two F₁ hydrids were used for these experiments, [B10.A(3R) x B10.A(5R)]F₁ and [B10.s(9R) x B10.HTT[F₁. F₁ macrophages responded equally well with F₁ T-B cells or with T-B cells of either parenteral strain. When F₁ macrophages were pretreated with anti-I-J serum (without complement) specific for one parenteral haplotype, they were only able to cooperate with T helper (Th) cells of the unblocked haplotype and with F₁ Th cells. Identical results were obtained with (J(b)xJ(k))F₁ and (J(s)xJ(k))F₁ mice. The results indicate that Th cells possess genetically restricted receptors for macrophage I-J-subregion gene products and that the interaction between this receptor and the macrophage I-J subregion determinant is essential for the initiation of a primary in vitro antibody response to an erythrocyte antigen.