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Clinical and Diagnostic Laboratory Immunology, May 2002, p. 677-686, Vol. 9, No. 3
1071-412X/02/$04.00+0     DOI: 10.1128/CDLI.9.3.677-686.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Low-Dose UVB Contributes to Host Resistance against Leishmania amazonensis Infection in Mice through Induction of Gamma Interferon and Tumor Necrosis Factor Alpha Cytokines

Departments of Dermatology,¹ Second Biochemistry,² Clinical Laboratory, Faculty of Medicine, University of the Ryukyus, Okinawa,³ Department of Parasitology, Kochi Medical School, Kochi, Japan,⁴ Department of Tropical Medicine, Faculty of Medicine, University of Catholic Santiago de Guayaquil, Guayaquil, Ecuador⁵

Received 31 May 2001/ Returned for modification 28 August 2001/ Accepted 14 December 2001

UV radiation suppresses the immune response, a fact which raises the question of whether the phenomenon may find practical applications in the outcome of infectious diseases. In this study, BALB/c mice were exposed to low-dose UVB (250 J/m²) from Dermaray M-DMR-100 for 4 consecutive days. Twelve hours after the last UV exposure, groups of mice were injected with 2 x 10⁶ Leishmania amazonensis promastigotes. The development of skin lesions, as assessed by measurement of visible cutaneous lesions, was significantly suppressed in low-dose UVB-irradiated mice compared to nonirradiated controls. In order to characterize the cytokines involved in this phenomenon, BALB/c mice were irradiated with identical doses of UVB, and gamma interferon (IFN-), tumor necrosis factor alpha (TNF-), and interleukin 4 cytokine levels in blood serum and skin were examined at different times by a sandwich enzyme-linked immunosorbent assay, immunohistochemical analysis, and reverse transcription (RT)-PCR. Upregulated expression of serum IFN- and TNF- was observed from 6 to 24 h. Positive results for IFN- and TNF- in UVB-irradiated mice were obtained by immunohistochemical analysis. By RT-PCR, the mRNA expression of both IFN- and TNF- cytokines was detected in a time-dependent manner only in UVB-irradiated mice. Histopathological analysis and electron microscopy revealed that cellular infiltration, tissue parasitism, and parasitophorus vacuoles in irradiated mice were markedly less noticeable than those in nonirradiated controls. These results suggested that low-dose UVB irradiation played a pathogen-suppressing role in Leishmania-susceptible BALB/c mice via systemic and local upregulation of Th1 (IFN- and TNF-) cytokines.

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