Effect of ultraviolet radiation on immunogenicity of tissues and organ allografts

Injection of mitomycin-C-treated spleen cells induces donor-specific unresponsiveness to cardiac allografts in rats

BACKGROUND

In this study, preoperative mitomycin-C- (MMC) treated donor-specific transfusion (DST) was examined for its ability to induce unresponsiveness to cardiac allografts in rats.

METHODS

DA (RT1a) rats were used as donors, BUF (RT1b) or WS (RT1k) rats as recipients, and Lew (RT1l) rats as third party donors. BUF or WS rats were given i.v. injection of DA spleen cells (SPCs) suspension (5x10(7)/l ml) with or without MMC treatment 10 days before cardiac transplantation. Delayed-type hypersensitivity and complement-dependent cytotoxicity assays were carried out in these animals separately to examine in vivo immunosuppressive effect. Suppressor assay was also examined to determine in vitro immunosuppressive effects in allogeneic mixed leukocyte culture.

RESULTS

In the full allogeneic DA-to-BUF rat strain combination, preoperative i.v. administration of MMC-treated donor SPCs led to a significant prolongation of graft survival over the control (110+/-66 versus 7.2+/-0.8 days: P<0.01), although administration of nontreated donor SPCs did not (9.3+/-1.0 days). This beneficial effect of MMC treatment was also seen in the DA-to-WS rat combination (31+/-16 days versus donor-specific transfusion alone; 11+/-1.5 days or untreated control; 12+/-1.5 days; P<0.05). However, injection of third party DA SPCs in the Lew-to-BUF combination induced no significant prolongation of cardiac allograft survival compared with the untreated control (11+/-0.6 versus 11+/-2.0 days; NS), indicating that this prolongation effect was induced in an antigen-specific manner. The immunosuppressive effect was also secured for both delayed-type hypersensitivity response and anti-donor cytotoxic antibody production. Moreover, addition of MMC-treated SPCs to mixed lymphocyte culture led to antigen-specific suppression.

CONCLUSIONS

Preoperative i.v. injection of MMC-treated donor SPCs is promising for inducing unresponsiveness in rat cardiac allograft model.

Transplantation of islets of Langerhans in patients with insulin-dependent diabetes mellitus

From 1974 to December, 1992, as reported by the International Islet Transplant Registry, there have been 175 adult islet allografts worldwide. Ninety-eight of these transplants have been performed since 1989. Eleven patients with Type I diabetes mellitus who have received islet allografts since 1989 have achieved insulin-independence for variable periods of time. As of June, 1993, four patients remain insulin-independent (from > 127 to > 326 days). Insulin-independence after human islet cell transplantation is not yet a consistent achievement. Several key issues in pancreas procurement, islet cell isolation, islet preservation, islet engraftment and the prevention of islet allograft rejection still need to be addressed. The expansion of current clinical trials should be limited to patients who are taking or who require immunosuppressive drugs for other reasons (kidney or liver transplant recipient) since the risks of chronic immunosuppression probably outweight the risks from chronic diabetes, although as we are able to induce a more specific state of immunosuppression this rationale may become debatable.

UV-B modulation of haplo-identical bone marrow cells in the prevention of GVHD and induction of specific transplantation tolerance to intestinal allografts

Ultraviolet B (UV-B) irradiation of BM cells (BMC) prior to transplantation into lethally gamma irradiated allogeneic rats prevents graft-versus-host disease (GVHD), induces stable allogeneic chimerism and specific tolerance to donor-type allografts. This study evaluated the role of UV-B modulation of bone marrow transplant (BMT) in the prevention of GVHD in the parent (P)-to-F1 hybrid rat combination of Lewis-to-Lewis x Brown Norway F1 (LBNF1) and of subsequent tolerance to small bowel transplantation (SBT). Lethally gamma irradiated (10.5 Gy) LBNF1 recipients of unmodified Lewis BMT (admixture of 10(8) BMC and 5 x 10(6) spleen cells) developed lethal GVHD and died within 55 days. Similarly, groups of lethally irradiated LBNF1 recipients of Lewis BMT treated with 100-300 J/m2 UV-B developed GVHD and died within 47 days. All F1 hybrid recipients of Lewis BMT treated with 700 or 900 J/m2 of UV-B permanently accepted their BM grafts, gained weight, showed no clinical evidence of GVHD and survived for > 300 days. These stable chimeras expressed 94-98% donor T-cells in their lymph nodes and became tolerant to BM donor-type (Lewis) SBT when grafted 180 days after BMT. In contrast, similarly prepared F1 recipients rejected BN SBT, thus demonstrating donor specificity. The chimeric rats were specifically unresponsive to donor (Lewis) Ag in MLR while they maintained normal alloreactivity to BN stimulators. These results suggest that UV-B irradiation of BMT offers a promising approach to overcoming the limitations of T-cell depletion of BMT and may offer a useful approach for recipient conditioning for induction of transplantation tolerance.

PUVA augments cyclosporine A-mediated rat cardiac allograft survival

PUVA, the administration of the photosensitizer 8-methoxypsoralen (8-MOP) followed by exposure of the skin to longwave ultraviolet radiation (UVA, 320-400 nm), is employed clinically for the treatment of skin diseases. PUVA is immunosuppressive and we have shown previously that it can significantly prolong skin allograft survival. This enhanced survival is associated with reduced spleen cell cytotoxic activity against donor cell targets with preserved ability of treated animals to be immunized to third-party alloantigens 5 days after exposure to a course of PUVA. To examine whether PUVA may potentiate the effect of cyclosporine A (CYA) in inhibiting cardiac allograft rejection, we employed a rat cardiac transplant model. Lewis rats (RT1(1) received cardiac allografts at a heterotopic site from Lewis Brown Norwegian (RT1(1/n)) hybrid donors. Seventy animals were equally divided into 10 groups. Starting on the day of surgery, three groups received a suboptimal doses of CYA (1.5, 4.5, or 9.0 mg/kg im), three groups received the same doses of CYA and 1.0 mg/kg of 8-MOP injected ip followed by 6.35 J/cm2 of UVA radiation to their shaved dorsums (PUVA), one group received PUVA alone, one group received UVA radiation alone, one group received 8-MOP alone, and the final group received no treatment. Therapy was carried out daily for 7 days and survival of the allograft was assessed by daily palpation of the transplanted heart.(ABSTRACT TRUNCATED AT 250 WORDS)