Chronic human skin graft rejection in severe combined immunodeficient mice engrafted with human PBL from an HLA-presensitized donor.

Mice with severe combined immunodeficiency (C.B-17 scid [SCID]) accepted xenografts of adult human peripheral blood leukocytes injected intraperitoneally as evidenced by production of human immunoglobulin (IgG and IgM), and circulation of human leukocytes in peripheral blood. SCID mice also accepted human split-thickness skin xenografts. Passenger leukocytes present in small numbers in such skin grafts could also recirculate in host peripheral blood and make detectable levels of human immunoglobulin. To test the immunocompetence of the transferred human PBL, SCID mice received a human skin xenograft from a second donor (HLA-mismatched with the PBL donor) either before (n = 6) or after (n = 23) xenografting of PBL. Skin was monitored daily for signs of rejection, and rejection was scored by histology 3-4 weeks after the second graft (PBL or skin) was placed. Of 19 SCID injected with PBL from an HLA presensitized patient (L.G.), 7/19 (37%) rejected a subsequent HLA-mismatched skin xenograft. Two of six SCID (33%) rejected a previously established skin xenograft when PBL were administered afterward. The rejection of the human skin was chronic, of relatively late onset (3-4 weeks), and was characterized grossly by contraction, glassy surface, and thickening. Histopathologic examination showed lymphocyte infiltration into the dermis with endothelial cell cuffing and destruction of capillaries, as well as lymphocyte tagging of the basal epidermis, hyperkeratosis, lymphocyte exocytosis and single epidermal cell necrosis. Immunostaining with monoclonal antibody to human CD2 or mouse CD3 revealed that human, but not mouse T lymphocytes were tagging the dermis/epidermis junction and infiltrating the epidermis of rejecting skin grafts. We conclude that a form of human skin graft rejection may be reproduced in an SCID mouse. The immune status of the transferred cells (sensitized vs. normal) and the lymphocytes ability to recirculate in SCID peripheral blood appear to be factors limiting the rejection process.