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Title: Mechanism of immunosuppression induced by ultraviolet-B light irradiation
Author: Moodycliffe, Angus M.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1993
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Irradiation with ultraviolet-B light (UV-B) suppresses some cell-mediated immune responses to a variety of antigens, including contact sensitizers. Following UV irradiation there is a modulation of Langerhans cell markers, and keratinocytes are induced to synthesize and secrete tumour necrosis factor-alpha (TNF-α). It has been postulated that there is a photoreceptor in the skin which mediates the effects of UV-B radiation on the immune system. One candidate is urocanic acid (UCA) found naturally in the stratum corneum of the epidermis as the trans-isomer, which converts to the cis-isomer on irradiation. Cis-UCA has been demonstrated to suppress immune reponses in several experimental systems. The mechanism of UV-B induced suppression of contact hypersensitivity (CH) responses and the role of cis-UCA were examined using a murine model of CH. UV-B irradiation was demonstrated to suppress the induction of CH response whilst cis-UCA had little, if any, effect. Next, the migration of dendritic cells (DC) to draining lymph nodes (DLN) following UV-B irradiation or epicutaneous application of UCA isomers was examined in unsensitized mice and mice sensitized with FITC. It was found that UV-B irradiation alone induced DC migration to DLN with a maximum number of DC being present in DLN 48 h following irradiation. In addition UV-B irradiation followed by skin sensitization at the same site enhanced DC migration. In sensitized mice, the percentage of DC bearing FITC and the quantity of FITC per DC were unaltered by prior UV exposure. Further, the percentage of DC expressing Ia or ICAM-1 molecules and the amount of Ia or ICAM-1 expressed per DC was unaffected by UV-B irradiation. In contrast to these results with UV-B irradiation, neither isomer of UCA had any significant effect on DC numbers in DLN in sensitized or unsensitized mice.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available