Differential control of allo-antigen-specific regulatory T cells and effector T cells by anti-CD4 and other agents in establishing transplantation tolerance

Abstract

Donor-specific graft tolerance can be established by a combination of allo-antigen exposure and manipulation of T cell function, for example by donor-specific transfusion (DST) under the cover of a non-depleting anti-CD4 mAb. Yet, the cellular basis of this graft tolerance is still obscure. This report shows that T cell-deficient BALB/c nude mice reconstituted with naive unfractionated T cells are specifically tolerized to DBA/2 skin grafts by DST and anti-CD4 mAb treatment, whereas those transferred with T cell suspensions depleted of all Foxp3+CD25+CD4+ natural regulatory T cells (Tregs) are not. The treatment inhibits Mls-1a allo-antigen-specific expansion of CD4+ non-Tregs expressing Vβ6 TCR subfamily but leaves the expansion of Vβ6-expressing Tregs unaffected, allowing the latter to selectively expand and establish donor-specific tolerance. Furthermore, anti-CD4 mAb inhibits in vitro the selective expansion of allo-antigen-specific CD4 non-Tregs but not natural Tregs, as observed with in vitro anti-CD154 [CD40 ligand (CD40L)] mAb or rapamycin treatment. The results collectively indicate that the differential effect of biologicals and pharmacological substances on the expansion of allo-antigen-specific Tregs and effector T cells and resulting dominance of the former can be a key general mechanism underlying dominant transplantation tolerance. © The Japanese Society for Immunology. 2009. All rights reserved.