Veto-like down-regulation of T helper cell reactivity in vivo by injection of semi-allogeneic spleen cells.

Injection of semiallogeneic (C57BL/6 X BALB/c) F1 MHC class II expressing spleen cells into C57BL/6 mice leads to a clonal deletion or anergy of recipient CD4+ T helper cells with specificity for the allogeneic MHC class II molecules on the injected cells whereas reactivity against third party allogeneic cells is not influenced. These observations were based on analyses in the recipient mice of proliferating CD4+ T cells in mixed lymphocyte reactions (MLR), limiting dilution (LD) cultures and measurements of IL-2 and IL-3 secretion.