Immune responses to implanted human collagen graft in rats

Immunity to collagen implants may be mediated by cellular and humoral immune responses. To examine the possibility of such immunological reactivity and crossreactivity to collagen, 39 Sprague-Dawley rats (female, 10 weeks old, approximately 250 g wt) were implanted subcutaneously at thigh sites with crosslinked, freeze-dried human placental type I collagen grafts (4 x 4 x 2 mm) which had been irradiated (520 Gray) or left untreated. Blood was obtained by intracardiac sampling prior to implantation or from normal rats, and at various times afterwards when the animals were sacrificed. The sera from these animals were examined for circulating antibodies to human, bovine and rat tail (type I) collagens by enzyme-linked immunosorbent assay (ELISA). Also, the lymphoblastogenic responses of spleen lymphocytes from the irradiated collagen-implanted animals were assessed in culture by measuring thymidine uptake with autologous and normal rat sera in the presence of human and bovine type I collagens. Implantation of the irradiated and non-irradiated collagen grafts in rats led to a significant increase in the level of circulating antibodies to human collagen. Also antibody to bovine and rat tail collagens was detectable in the animals implanted with irradiated collagen grafts but at a lower level than the human collagen. There was a raised lymphoblastogenic response to both human and bovine collagens. The antibody level and lymphoblastogenesis to the tested collagens gradually decreased towards the end of the post-implantation period.