Specific and nonspecific infiltration of sponge matrix allografts by specifically sensitized cytotoxic lymphocytes

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Urethane sponges coated with allogeneic or syngeneic cells were implanted subcutaneously into mice and the cytotoxicity of infiltrating host cells was assessed in vitro. First-set allogeneic sponges attracted a population of lymphocytes enriched in cytotoxic T cells directed against the alloantigens in the sponge. If two sponges bearing cells of different H-2 specificity were grafted simultaneously to a single recipient, specifically sensitized cytotoxic cells (SSCL) were found in both sponges directed against both sets of alloantigens, although specific infiltration predominated. If a syngeneic and allogeneic sponge were transplanted, SSCL were found in both the syngeneic sponge and allogeneic sponge. These data are interpreted to suggest that chemotactic substances are elaborated at graft sites which can attract circulating SSCL into sites of inflammation and that those released at the specific site are more attractive for SSCL than are those elaborated at sites of nonspecific rejection or healing. In recipients who had previously been sensitized to alloantigens, second-set grafts were rapidly infiltrated by SSCL directed against the sensitizing antigen. First-set indifferent allografts in sensitized recipients were infiltrated by SSCL directed against the previous alloantigens as well as SSCL directed against its own alloantigens. Syngeneic grafts were not infiltrated by SSCL in presensitized recipients. These data suggest that any alloantigenic stimulus can induce the mobilization from lymphoid depots of preformed SSCL directed against another set of antigens; syngeneic grafts cannot. Once mobilized, however, circulating SSCL can respond to specific and nonspecific chemotactic factors elaborated by either healing or rejecting grafts.