To explore the efficacy of ultraviolet B-irradiated donor-specific leukocyte transfusions (UV-DSLT) with short-term cyclosporine to control intestinal allograft rejection, 75 adult Lewis (RT1l) rats underwent total small-intestinal transplantation from Brown-Norway (RT1n) donors. Recipients were randomly divided into ten treatment and control groups utilizing various combinations of donor-specific and third-party (Wistar-Furth, RT1u) leukocyte transfusions (TPLT), with or without transfusion UVB irradiation, and either alone or in combination with short-term cyclosporine administration (5 mg/kg intramuscularly on days -7, 0, 1, and 2 relative to transplantation). Leukocytes (10(8) cells) separated from a spleen cell suspension were infused on day -7. Certain transfused leukocytes were treated with 12,000 joules/m2 of UVB irradiation. Groups were monitored for mean survival time (MST) and cause of death. UV-DSLT alone (MST = 19.8 +/- 4.6) or in combination with cyclosporine (UV-DSLT+CsA, MST = 53.1 +/- 22.5) significantly (P less than 0.003-0.0002, Mantel-Cox) prolonged recipient survival when compared with appropriate controls (i.e., no treatment, MST = 11.2 +/- 3.4; CsA, MST = 17.2 +/- 9.0; UV-TPLT, MST = 12.4 +/- 4.0; and UV-TPLT+CsA, MST = 25.1 +/- 9.7) No significant increase in graft-versus-host disease occurred in any group, with 85% (64/75) of the recipients dying of acute rejection. Conversely, the UV-DSLT+CsA group had a significant increase (9/11; chi-square, P less than 0.0001) in chronic rejection. Because UV-DSLT+CsA improved survival as compared with third-party controls, a limited donor-specific unresponsiveness may have been induced. Furthermore, this treatment produces a consistent, chronic rejection rodent intestinal allograft model.