Ultraviolet irradiation in transplantation biology. Manipulation of immunity and immunogenicity.

Ultraviolet irradiation, particularly in the UVB range, has profound effects on immunological mechanisms. Optimum and tolerable doses of exposure vary from species to species, and from organ to organ. As a result of limited depth penetration and possibly significant energy absorption in nontargeted cells, every model requires diligent determination of an effective nontoxic approach. Nevertheless, it is clear that UVB and UVC irradiation can abolish proliferative and stimulatory ability as well as accessory/antigen-presenting ability of leukocytes in vitro. UV treatment alters cell-surface properties, calcium mobilization, cytokine production and release, and other subcellular processes. Preliminary data suggest that these manipulations also suppress immunity and reduce immunogenicity in vivo. Exposure of solid organs and of large volumes of blood is difficult due to technical problems--in particular poor depth penetration and absorption of UV energy in generally available transfusion bags.