Predominant expression of the Th2 response in chronic cardiac allograft rejection

Chronic rejection is the main cause of late allograft failure in patients. CD4+ T cells activated by indirect recognition of alloantigens are implicated in this rejection reaction. However, the type of T cell response (Th1 vs Th2) that contributes to chronic rejection has not been fully investigated. The purpose of this study is to examine whether chronic rejection is associated with a polarized T-cell response in a rat cardiac allograft model, where long-term graft survival is achieved by intrathymic immunomodulation with donor class I, RT1.Aa, allopeptides. All long-surviving allografts showed histological evidence of chronic rejection. Chronic rejection was associated with high levels of intragraft Th2 cytokines and the Th2-regulated alloantibodies. The Th2 response was systemic, since long-surviving allografts with chronic rejection had high levels of serum IL-10. The predominance of the Th2 cytokines demonstrates that the Th2 response was not sufficient for the prevention of chronic rejection in this model. The predominant expression of Th2 cytokines, together with the presence of Th2-regulated alloantibodies, suggests that the Th2 response may play a role in the development of chronic rejection.