THE HUMORAL RESPONSE TO VASCULAR AND NONVASCULAR ALLOGRAFTS OF BONE

The cytotoxic, donor specific antibody response after vascularized and nonvascularized bone allograft implantation was assessed in rats and dogs. Nonvascularized segmental femoral grafts were studied in rats; n onvascularized fresh and cryopreserved massive osteochondral allograft s were studied in dogs; and vascularized and nonvascularized fibular a llografts were studied in dogs. The major histocompatibility complex a ntigens of all animals were defined. All grafts were stabilized by int ernal fixation and the antibody response was measured in a 5'chromium release microcytotoxicity assay using donor lymphocytes as target cell s. In all cases, donor specific antibody responses were elicited by ma jor histocompatibility complex mismatched fresh grafts. The response w as directed primarily at Class I specificities although there was like ly an antiClass II response as well. Among fully mismatched grafts, an tidonor antibody was detectable earlier in animals receiving vasculari zed grafts (1 week after surgery) than in animals receiving nonvascula rized grafts (3 weeks after surgery). Massive grafts elicited a sustai ned response whereas relatively smaller grafts, such as the fibula, di d not. The antidonor antigen antibody response was transient and less frequent in animals receiving frozen grafts, The clinical implications of these data are unclear Although some improvement of clinical outco me has been observed with grafts matched for major histocompatibility complex antigens, the potential benefits of tissue antigen matching of modulation of the host immune response remain unresolved.