The Role of NK Cells in the Elicitation Phase of Oxazolone Inducing Contact Hypersensitivity

We studied the role of infiltrating cells and cytokines synthesis in oxazolone (OXA)-induced contact hypersensitivity (CHS) of C57BL/6 mouse ear model. The cell mediate lesion was induced by the OXA challenge after abdominal skin sensitization, and those of infiltrating cells were examined at various time points (0-168 hr). The CHS lesions were indicated as an ear swelling at 24 to 48 hr after the challenge that was caused mainly by infiltration of mononuclear cells expressing CD90+, CD4+ and CD8+. However, NK cells by means of asialo GM1+ cells, were detected in the lesions as early as 2 hr after challenge. The infiltration of NK cells peaked at 8 hr and replaced in the predominant accumulation of polymorphonuclear (PMN) cells and some of CD90+ cells. Cytokine expression of the infiltrating cells by RT-PCR, revealed a high level of IL-2 expression at 8, 12, and 24 hr and then reduced expression in the following times, while, IFN-γ was constantly detected from 2 hr to 168 hr. Deletion of the NK cell activity by administration of the anti-asialo GM1 antibody resulted in significantly suppressed cell infiltration and ear swelling. IL-2 mRNA expression was undetected in the infiltrating cells of deletion mouse, whereas IFN-γ was detected at 12, 24, and 48 hr. The presence of NK cells as the first infiltrating cells in the lesion and IL-2 and INF-γ synthesis from the infiltrating cells may play an important role in the elicitation phase of CHS.