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Bone marrow mononuclear cell (BMMC) transplant may serve to produce donor specific tolerance for a coincident solid organ graft, but with the risk of graft versus host disease (GVHD). We examined in vitro the immunomodulatory effect of UVB on human BMMCs as potential prophylaxis against GVHD for clinical transplantation. After 10-200 J/m2 UVB-irradiation, BMMCs were examined by proliferative response (in mixed lymphocyte reaction and following phytohemagglutinin stimulation) and by cytokine profile. We also evaluated CFU-GM, CFU-GEMM, and BFU-E progenitor viability by 2-week methyl cellulose cultures following UVB-irradiation. Parallel studies were applied to marrow that was T-cell depleted by soybean agglutination (SBA) or by SBA and sheep erythrocyte rosetting (SBA-E-). We found that (1) UVB produces a dose-dependent inhibition of the proliferative response to stimulators by human BMMCs; (2) increasing doses of UVB-irradiation and increasing levels of T-cell depletion (TCD) are both inversely related to production of lymphokines (IL2, IL3, LIF, IFN-gamma, and GMCSF) and (3) T-cell depletion, but not UVB-irradiation, decreases the production of monokines (IL1, TNF, IL6). Progenitor cell viability was decreased but preserved at 100 J/m2 of UVB. Our findings suggest that UVB compares favorably with TCD as a technique for inhibition of GVHD and therefore that UVB-modulation of bone marrow (BM) inoculum may be useful in the prevention of GVHD in clinical bone marrow transplantation accompanying a solid organ graft.

We have previously demonstrated that Ultraviolet B (UVB) irradiation of Lewis donor bone marrow (BM) allografts prevents graft versus host disease (GVHD) in ACI recipients while allowing full engraftment. In a one-way GVHD model of parent to Lewis X BN (F1) rats, the site and mechanism of the action of UVB irradiation was assessed by adding nonirradiated isolated cell subsets, isolated by monoclonal antibodies (Mab) to cell surface markers, to the reconstituting UVB-irradiated bone marrow inoculum. GVHD was assessed primarily on clinical grounds by observation of posture, alopecia, skin erythema, and weight loss. The addition of nonirradiated spleen cells or non-UVB-irradiated T-cell subsets (both CD4 and CD8 positive) to the otherwise UVB-irradiated donor inoculum consistently resulted in acute GVHD. In contrast, UVB irradiation of these cells resulted in full engraftment without acute GVHD. Mixed lymphocyte culture (MLC) assays confirmed responsiveness by BM transplanted hosts to third party stimulators while coculture assays failed to show any in vitro suppressor activity in the host. We conclude that UVB acts on both the T-lymphocyte and antigen presenting cell (APC) subsets to prevent acute GVHD. We also propose a model to explain tolerance based on clonal anergy produced by modified antigen presentation by UVB-irradiated APC's or by a modified response to processed antigen.

This study extends the finding that intrathymic (IT) inoculation of uv-B irradiated donor spleen cells (SC) or soluble alloantigens (Ag) induces peripheral tolerance to organ allografts in the rat to the murine cardiac allograft model. In our initial experiment, we showed that IT inoculation of uv-B irradiated SC combined with transient immunosuppression of the recipient with either sublethal TBI or ALS on Day -7 led to donor-specific, long-term cardiac allograft survival (> 300 days) in the completely mismatched A/J-to-C57BL/6 mice combination. To test our hypothesis that peripheral tolerance induced by IT injection of donor Ag is dependent on presentation of the foreign MHC molecule by thymic APC to T cell precursors, we examined the effect of IT injection of donor APC-free-soluble Ag inoculum obtained from 3 MKCl extracts of purified MHC class I resting T cells on cardiac allograft survival in the A/J-to-C3H mice combination. The results showed that IT injection of the optimal dose of 500 micrograms soluble Ag combined with 0.5 ml ALS on Day -7 led to donor-specific permanent graft survival (> 200 days). This finding could not be reproduced by intravenous administration of soluble Ag, thus confirming the privileged position of the thymus in tolerance induction. To further define the role of host APC in allorecognition, we studied the presentation of soluble Ag by responder APC in MLR. The results showed that primed T cells obtained from A/J skin graft-sensitized C3H T cells specifically developed alloreactivity to A/J-soluble Ag in MLR.(ABSTRACT TRUNCATED AT 250 WORDS)

We have shown that donor-specific unresponsiveness to cardiac and islet allografts can be induced by intrathymic (IT) inoculation of uv-B-irradiated spleen cells or resting T-cells in the Lewis-to-ACI rat combination. To examine if tolerance to cardiac and small intestinal allografts can be induced in adult animals, we employed intrathymic inoculation of resting donor T-cells combined with sublethal total body irradiation of 200 rads on Day -7 relative to organ transplant and consistently induced permanent donor-specific cardiac allograft survival (> 300 days) and small bowel transplant (SBT) survival (> 100 days) in the Lewis-to-ACI rat combination. Similarly, IT inoculation of T-cells on Day -7 combined with 1 ml ALS on Days -7 and 0 relative to SBT resulted in indefinite donor-specific graft survival (> 100 days) in all recipients without any evidence of graft-versus-host disease (GVHD) in the high responder of Wistar-Furth (WF)-to-Lewis rat combination. In contrast, WF SBT was promptly rejected in recipients pretreated with intravenous administration of donor T-cells and ALS, thus confirming the privileged position of the thymus in the induction of tolerance. The long-term unresponsive ACI recipients challenged 150 days after cardiac transplant with a second-set graft specifically and permanently (> 120 days) accepted the second-set SBT without rejecting the primary cardiac grafts and without developing GVHD. Third-party grafts were rejected in a normal fashion.(ABSTRACT TRUNCATED AT 250 WORDS)