Influence of ultraviolet radiation treatment on the survival of heterotopic skin grafts in the mouse

Characterization of graft-versus-host disease in SCID mice and prevention by physicochemical stressors

BACKGROUND

Graft versus host disease (GVHD) prevents potentially curative allogeneic stem cell transplantation from being offered to cancer patients who lack a suitably matched donor. New methods to prevent GVHD are required to allow successful transplants across major histocompatibility complex barriers.

METHODS

A model of GVHD in C.B-17 SCID mice was developed to allow the study of allo-activated donor T cells without confounding effects of host lymphocytes. The abilities of cyclosporin-A, anticytokine antibodies, and oxidative stress to prevent GVHD in this model was studied.

RESULTS

T cells from major histocompatibility-mismatched donor mice caused severe GVHD in sublethally irradiated SCID hosts that could be ameliorated by coadministration of donor bone marrow but not by cyclosporine-A or anticytokine antibodies. In contrast, three-log more T cells could be injected without clinical consequences if they had been pretreated with a combination of heat, ultraviolet light, and oxygenation. The effect was not the trivial result of donor T cell destruction because T cell reconstitution, although delayed, recovered to normal levels within 2 weeks. Protection from GVHD required oxygenation and was associated with normalization of the CD4/CD8 donor T cell ratio, recovery of host hematopoiesis, and decreased inflammatory cytokine production.

CONCLUSION

Pretreatment of donor T cells with a combination of physicochemical stressors effectively prevents GVHD caused by major major histocompatibility disparities and may facilitate the safe transplantation of patients without HLA-identical donors.

Modulation of HLA-DR and CD1a expression on human cornea with low-dose UVB irradiation

PURPOSE

To evaluate the effects of low-dose UVB irradiation of HLA and CD1a expression and the toxic effects of UVB on human corneas.

METHODS

24 pairs of human corneas from 24 donors were studied. One cornea from each pair was randomly irradiated with UVB (100 mJ/cm2) after enucleation. All corneas were then organ-cultured for 2, 7, 14 or 21 days. Endothelium was studied after enucleation and organ culture. Following preservation, corneas were evaluated by means of light microscopy, morphometry and TEM. HLA and CD1a staining was performed using an immuno-alkaline-phosphatase technique.

RESULTS

Endothelial cell loss during organ culture averaged 9.1% in the UVB group and 9.2% in the control group (NS). The number of rosette and reformation figures (p = 0.004) and the coefficient of variation (p = 0.014) were higher in the control group. Epithelial sloughing was more accentuated in the UVB group. We observed the same moderate ultrastructural injuries in both groups. In the epithelium, the average number of HLA-DR+ cells per field was 0.12 in the UVB group and 0.42 in the control group (p = 0.035). In the stroma, these figures were respectively 1.04 and 1.34 (p = 0.026). In the epithelium, the average number of CD1a + cells was respectively 0. 025 and 0.078 (p = 0.019). In the preservation mediums, the average percentage of CD1a + cells was 0.07% in the UVB group and 0.27% in the control group (p = 0.014).

CONCLUSIONS

Low-dose UVB (100 mJ/cm2) decreases HLA-DR and CD1a expression of organ-cultured human corneas and induces moderate corneal injuries. Low-dose UVB might be useful for preventing allograft rejection.

Abrogation of allospecific T lymphocyte responses in swine by ultraviolet light-B irradiation

Immunomodulatory effects of ultraviolet-light B (UV-B) irradiation were tested in pigs, using peripheral blood lymphocytes (PBL), with special emphasis on the generation of cytotoxic T lymphocytes (CTL). Stimulator PBL were irradiated with 300-1100 Joules/m2 (J/m2) of UV-B (experimental group) and cultured for 24 h prior to being placed in mixed lymphocyte culture (MLC) to determine proliferative responses against alloantigens, or placed in bulk culture with allogeneic PBL to determine the induction of CTL. PBL that received 3000 rads gamma irradiation were used as controls. Proliferative alloresponses against gamma irradiated PBL (control group) were high, with stimulation indices (S.I.) ranging from 13.46 to 81.93. The generation of allospecific CTL activity was also high, ranging from 50.78% to 95.40%. In contrast, proliferative responses and generation of allospecific CTL were markedly inhibited (> 49.77%) against the same donor PBL irradiated with > or = 500 J/m2 UV-B. These results demonstrated that ultraviolet light treatment of pig PBL can reduce or prevent allospecific T cell proliferation as well as the generation of specific CTL, similar to results obtained with UV-B irradiation of lymphocytes in rodents.

Immunomodulation of vascular endothelium. 1. Ultrastructural changes following ultraviolet B irradiation of peripheral veins

Immunologic function of endothelial cells is especially important in consideration of vein allografting for arterial reconstruction and in organ allotransplantation. Ultraviolet B radiation (UVB) has previously been shown to modulate graft immunogenicity, and to alter cell surface receptor function. In this study, superficial epigastric veins were UVB irradiated with 10, 24, 40, 80, and 150 mJ/cm2 while control veins were not irradiated; all specimens were examined for endothelial ultrastructural changes. Veins were perfuse-fixed at 1, 3, 7, 14, and 28 days after irradiation, and were evaluated by transmission electron microscopy and scanning electron microscopy. Control veins had a normal appearing endothelial lining, composed of elongated, attenuated endothelial cells. Veins irradiated with more than 24 mJ/cm2 displayed injured endothelial cells characterized by altered microvilli, defects in the cell surface, and a change in cell shape. The degree of cell damage correlated closely with increasing UVB dose. At doses of 80 mJ/cm2 or greater there was moderate to severe endothelial cell separation from the underlying basement membrane and an increase in cellular lysosomes. The effects of UVB were maximal at 3 days with virtual recovery in resurfacing of all specimens with endothelium 28 days after irradiation. These data suggest that UVB has a dose-dependent effect on venous endothelium that is morphologically reversible with time. Cell membrane changes seen following exposure to UVB may contribute to altered cell surface receptor function.

Antigen-presenting cells in the induction of contact hypersensitivity in mice: evidence that Langerhans cells are sufficient but not required

One explanation for the fact that certain genetically defined strains of mice prove to be resistant to effects of low dose ultraviolet B radiation on the induction of contact hypersensitivity is that ultraviolet B resistant mice possess a second pathway for antigen presentation through the skin--a pathway that is independent of epidermal Langerhans cells and beyond the reach of the damaging effects of ultraviolet B light. As a corollary, ultraviolet-B susceptible mice would be expected to be deficient in this pathway. Several experimental strategies were employed to determine whether Langerhans cells are required for the induction of contact hypersensitivity by epicutaneously applied hapten. The results reveal that tape-stripped skin supports the induction of contact hypersensitivity, whereas surgical excision of hapten-painted skin within 1 h of application fails to permit the development of contact hypersensitivity. Because the former selectively eliminates epidermal Langerhans cells while the latter deletes both Langerhans cells and dermal antigen-presenting cells, we conclude that either Langerhans cells or dermal cells are sufficient to provide antigen presentation in the induction of contact hypersensitivity. When large amounts of hapten are painted epicutaneously, or when hapten is injected subcutaneously or painted on sub-dermal tissues, contact hypersensitivity also results, indicating that induction of contact hypersensitivity does not require that antigen processing and presentation be provided by cutaneous cells. Reasons are presented for concluding that under physiologic circumstances induction of contact hypersensitivity by epicutaneous hapten application relies primarily upon the antigen-presenting capabilities of epidermal (Langerhans cells) and dermal cells.

Alloimmunization after leukocyte-depleted multiple random donor platelet transfusions

In a prospective study we investigated the development and the course of alloimmunization after leukocyte-depleted red cell and multiple random donor platelet transfusions in 335 patients. Of these 335 patients, who had a negative antibody screening on admission and a negative transfusion history, 69 (21%) developed either transient (n = 18) or permanent (n = 51) lymphocytotoxic antibodies, but only 31 patients (9%; 95% confidence limits 6-12%) developed multispecific alloantibodies necessitating HLA-matched platelet transfusions. There was no difference with regard to the development of antibodies and platelet refractoriness between leukemia patients receiving cytostatic treatment and patients with aplastic anemia receiving prednisone and antithymocyte globulin. Females with previous pregnancies developed platelet refractoriness with an increased incidence (Chi 2 13.38; p less than 0.001) compared to females without previous pregnancies, males, and children.