Chronic rejection in H‐2 matched cardiac allografts: early emergence of vasculopathy, alloantibody, and accumulation of IFN‐γ and IL‐10 mRNA

Cardiac allograft vasculopathy (CAV) is one of the crucial problems of clinical heart transplantation. We have developed a novel model of murine cardiac allograft rejection, in which chronic rejection associated with CAV occurs in its natural course. In this study we analyzed the pathogenesis of chronic cardiac allograft rejection using an H-2 matched multiple minor histocompatibility antigen-mismatched combination, AKR (H-2k) to C3H (H-2k) recipient mice. All the cardiac allografts survived for more than 100 days but were rejected within 260 days post-transplant (n = 13; mean survival times ± standard deviation = 189.0 ± 72.0; median = 210). The heartbeats of the graft became gradually weaker throughout the duration of the rejection process. Serial histological analyses with hematoxylin and eosin, elastica van Gieson or Masson trichrome staining revealed mononuclear cell infiltration and intimal thickening (i. e. CAV) which started in most grafts at 2 weeks post-transplant. These pathological changes eventually developed to severe graft fibrosis, and the severity of these changes correlated with the deterioration of the heartbeats. Production of anti-donor antibodies in most recipients was detectable by 2 weeks post-transplant, it peaked before day 100, and subsided before rejection was complete in most grafts. Intragraft expression of IFN-γ and IL-10 mRNA was demonstrated by reverse transcriptase-polymerase chain reaction during early periods post-transplant. In this study, we demonstrate a novel model feasible for analysis of chronic cardiac allograft rejection, in which the vascular rejection processes, including fibrosis and alloantibody production, can be tested from an early stage on, after transplantation.