Superagonist CD28 antibody preferentially expanded Foxp3-expressing nTreg cells and prevented graft-versus-host diseases.

Regulatory lymphocytes play a pivotal role in preventing organ-specific autoimmune disease and in induction and maintenance of tolerance in various experimental transplantation models. The enhancement of the number and activity of peripheral CD4(+)CD25(+) Treg cells is an obvious goal for the treatment of autoimmunity and for the suppression of alloreactions. The present study demonstrates that naturally occurring CD4(+)CD25(+) Treg (nTreg) cells preferentially proliferate to a fourfold increase within 3 days in response to the administration of a single superagonistic CD28-specific monoclonal antibody (supCD28 mAb). The appearance of increased Foxp3 molecules was accompanied with polarization toward a Th2 cytokine profile with decreased production of IFN-gamma and increased production of IL-4 and IL-10 in the expanded Treg subset. Adoptive transfer of supCD28 mAb-expanded cells in a graft-versus-host disease (GvHD) model induced a potent inhibition of lethality. These results suggest that this therapeutic effect is mediated by the in vivo expansion of nTreg cells. Taken together, these data demonstrate that supCD28-mAb may target nTreg cells in vivo and maintain and enhance their potent regulatory functions for the treatment GvHD.