29th Annual Meeting of the American Society of Photobiology

Downtown Marriot

Chicago, Il.

July 7th-12th, 2001

Protection of the Delayed Type Hypersensitivity Immune Response to Candida Albicans and Alloantigen from Suppression by Chronic UV Radiation

Strickland, Faith1 and Darvill, Alan 2
The University of Texas M. D. Anderson Cancer Center, Houston, TX 770301
Complex Carbohydrate Research Center, The University of Georgia, Athens, GA2

Abstract-
Model systems designed to clarify the mechanism of immune suppression by UV radiation showed that a single exposure to a low (2 kJ/m2) dose of UVB radiation (280-320nm) locally inhibited the induction of contact hypersensitivity responses to hapten while higher doses systemically inhibited delayed type hypersensitivity (DTH) responses to Candida albicans and alloantigen. The suppressive effects of UV radiation on responses to hapten and C. albicans are triggered by a DNA-damage pathway while suppression of immunity to alloantigen is regulated through the cis-urocanic acid pathway. Tamarind seed xyloglucans (TXG) prevent suppression of immunity to both C. albicans and alloantigen but not hapten by a single dose of UV radiation. We investigated the ability of TXG to prevent suppression of T cell-mediated immune responses and suppressor cell induction during chronic UV irradiation. The shaved dorsal skin of C3H/HeN mice was exposure to 15 kJ/m2 UVB radiation from FS40 sunlamps 3 times per week. Immediately following each UV exposure the dorsal skin of the mice was treated with 1g/mouse TXG in PBS vehicle. Matching control animals were treated with TXG but were not UV-irradiated. DTH responses to C. albicans and alloantigen were measured after 1, 6 and 12 weeks of treatment. TXG protected immunity to C. albicans for up to 6 weeks of UV radiation after which protection declined and suppressor cells were observed. In contrast, TXG preserved DTH immunity to alloantigen for the entire 12 weeks of UV irradiation. The results suggest that there are significant differences between results obtained from single versus chronic UV treatment, and that the regulation of T cell immunity by the two pathways is complex and may not be simply related to the dose of UV given.

Keywords: tolerance, ultraviolet, T lymphocytes, polysaccharide