Nature of macrophage‐T cell interaction in secondary helper cell generation in vitro Genetic restriction of macrophage‐T cell interaction, which determines T‐B genetic restriction

Abstract

To investigate the histocompatibility requirements for the macrophage-T cell interaction in the secondary antibody response, splenic T cells from antigen (carrier)-primed F₁ hybrid mice were restimulated in vitro with carrier-pulsed F₁, parental or allogeneic macrophages. Surviving T cells were cocultured with hapten-primed F₁ or parental “B cells” and restimulated with the appropriate hapten-carrier conjugate. The IgG antibody-forming cell response was then measured using a plaque assay. Mapping of the genetic restriction was performed by use of different strain combinations. T helper cells could be restimulated in the presence of macrophages only provided they shared the I-A subregion of the major histocompatibility complex with the F₁ T cells. T cells from F₁ hybrids restimulated with parental or I-A-identical macrophages were shown to only cooperate with parental B cells of the same I-A haplotype as the macrophages used for restimulation. The defect was at the level of the macrophage, as addition of macrophages of the I-A haplotype used for the restimulation culture reconstituted the ability of F₁ helper cells to cooperate with the I-A-nonidentical B cells.