(TG)-A--L-primed T cells from high responder × low responder F1 mice induced high anti-TNP responses to TNP-(TG)-A--L in vitro in B cells and macrophages (Mϕ) from the high responder parent, but low responses in B cells and Mϕ from the low responder parent. Mixing experiments established that high responsiveness required the presence of both high responder B cells and Mϕ in the cultures demonstrating the expression of Ir-genes in both of these cell types.
Irradiation chimeras were prepared by transferring parental bone marrow into irradiated F1 recipients. (TG)-A--L-primed T cells bearing the low responder H-2 type were isolated from these chimeras and shown to induce high responses in vitro with high responder B cells and Mϕ. Thus, it was not obligatory that helper T cells carry the high responder Ir-gene in order to obtain a high response.
Irradiation chimeras were prepared by transferring F1 bone marrow into irradiated low responder parental mice.