Background: Our goal was to test the intragraft mRNA expression and production of two chemokines that are potent chemoattractants for antigen-primed T cells, interferon-gamma inducible protein 10 (IP-10) and monokine-induced by IFN-gamma, (Mig), in allogeneic heart grafts.
Methods: Syngeneic or allogeneic A/J (H-2a) hearts were heterotopically transplanted to wild-type, CD4-/-, CD8alpha-/-, or IFN-gamma-/- C57BL/6 (H-2b) recipients. To test expression of IP-10 and Mig, grafts were removed 1-8 days posttransplant for RNA isolation and Northern blot analysis. To test the potential recipient leukocyte populations mediating intraallograft expression of IP-10 and Mig, recipients were treated with anti-NK 1.1, anti-CD4, and/or anti-CD8 monoclonal antibodies before transplantation.
Results: Allogeneic heart grafts transplanted to wild-type, but not IFN-gamma-/-, recipients expressed IP-10 and Mig at day +2 posttransplant that increased thereafter until rejection was completed. Expression of IP-10 and Mig in isografts was low or undetectable. Cardiac allografts from CD8+ T cell depleted, but not NK cell or CD4+ T cell depleted, recipients had low to undetectable expression of IP-10 and Mig on day +2 posttransplant. Similarly, cardiac allografts from CD8-/-, but not CD4-/-, recipients had low to undetectable expression of IP-10 and Mig on day +2 posttransplant.
Conclusions: Early intraallograft expression of Mig and IP-10 during primary rejection of cardiac allografts is dependent on the activities of recipient CD8+ T cells.