Increased expression of transforming growth factor-β and eosinophil infiltration is associated with the development of transplant arteriosclerosis in long-term surviving cardiac allografts

Background. Transplant arteriosclerosis is a major limiting factor for long-term function of allografts in clinical transplantation. This study investigated the impact of three different protocols capable of inducing long-term allograft survival on the development of transplant arteriosclerosis and immune response in cardiac allografts. Methods. CBA.Ca (H2^k) recipients of fully allogeneic C57/BL10 (H2^b) heart grafts received a short-term course of anti-CD154 antibody or were pretreated with anti-CD4 antibody in combination with donor alloantigen in the form of CBK (H2 ^k+K^b) bone marrow or C57BL/10 donor-specific transfusion (DST). Grafts were analyzed on day 40 or 100 after transplantation for transplant arteriosclerosis and expression of interferon-γ, interleukin (IL)-2, IL-4, IL-10, IL-12p40, inducible nitric oxide synthase, and transforming growth factor (TGF)-β1 mRNA. Serum was analyzed for the presence of alloantibodies. Results. Intimal proliferation was 62%±11% on day 40 in the anti-CD154 group, progressed from 31%±10% on day 40 to 68%±8% on day 100 in the CBK-bone marrow group, but remained stable at 39%±4% in the DST group. Increased transplant arteriosclerosis on day 100 was associated with high intragraft TGF-β₁ mRNA production and eosinophil infiltration, but not alloantibody production. Progressing transplant arteriosclerosis was associated with increased IL-4 expression. Conclusion. Treatment protocols for the induction of long-term allograft survival can differ substantially in the extent and kinetics of transplant arteriosclerosis. IL-4 and TGF-β₁ may be two potential therapeutic targets to attenuate the development of transplant arteriosclerosis in the long term.