INTRAGRAFT EXPRESSION OF RANTES IS ASSOCIATED WITH GRANZYME B AND T CELL MEDIATED CYTOTOXICITY DURING REJECTION OF ALLOGENEIC SKIN GRAFTS

Abstract

135 OBJECTIVE: Previous results from this lab indicated intragraft RANTES expression 3 days before rejection of skin allografts in mice. This expression occurred during rejection of fully allogeneic grafts and grafts disparate at single class I, but not single class II, MHC loci, suggesting that CD8+ T cells may be required for this expression. The goal of this study was to identify the T cells required for the expression of RANTES during rejection of skin grafts. METHODS: C57BL/6 (H-2b) mice received trunk skin grafts from syngeneic and allogeneic donors, including BALB/c (H-2d), H-2bm1, H-2bm12, BALB.B(H-2b) mice. Mice with targeted deletions in the genes encoding perforin (p-/-) or CD8α (CD8-/-) on the C57BL/6 background were also tested as recipients. Groups of recipients were depleted of T cell populations by treatment with anti-CD4 or anti-CD8 antibody before and after transplantation. Grafts were removed 1-5 days before rejection was complete for RNA isolation and Northern blot analysis. RESULTS: Intragraft expression of RANTES was prominent in BALB/c and bm1 grafts on both C57BL/6 wild-type and p-/- recipients by 5 days before rejection and levels increased until rejection was complete. Depletion of CD8+ T cells from C57BL/6 recipients of BALB/c grafts delayed intragraft expression of RANTES until 1 day before rejection was complete. Expression was not detected in BALB/c grafts rejected by CD8-/- recipients. Strong expression of RANTES was also observed in BALB.B grafts but not until 1 day before rejection was complete. Expression of RANTES was not detectable in bm12 grafts until 1 day before rejection and at very low levels. Expression of RANTES was not detected in isografts. Intra-allograft expression of granzyme B paralled that of RANTES in each of the donor → recipient combinations tested. Furthermore, intragraft expression of RANTES and granzyme B during rejection was associated with the ability of recipient CD4+ and/or CD8+ T cells to mediate cytolysis of donor target cells. CONCLUSIONS: Intragraft expression of RANTES is observed during either CD4+ or CD8+ T cell mediated rejection and is associated with granzyme B mediated cytolysis during allograft rejection. The absence of RANTES expression during rejection of some allografts indicates that it is not required during the graft rejection process.