Reduced production of both Th1 and Tc1 lymphocyte subsets in atopic dermatitis (AD)

An imbalance of interferon-gamma (IFN-gamma)-bearing CD4+ T (Th1) cells in the pathogenesis of AD is well recognized; however, a possible role in AD for CD8+ T cells secreting Th1-like cytokines (Tc1) has not been properly addressed. In this study, two- and three-colour FACS analysis allowed us to discriminate the Th1 from the Tc1 subset. AD patients had half the number of IFN-gamma-producing circulating T cells (P < 0.005; 13.6 +/- 1.9% (mean +/- s.d.)) compared with normal donors (25.0 +/- 2.4%). Specifically, both Th1 (4.8 +/- 0.7%) and Tc1 (8.1 +/- 1.1%) cells in AD were decreased compared with Th1 (8.8 +/- 0.8%) and Tc1 (15.0 +/- 1.5%) cells in controls. Moreover, at the mRNA level, the ratios of IFN-gamma/IL-4 and IFN-gamma/IL-10 were lower in cells from AD patients compared with controls. In conclusion, the decrease of IFN-gamma-producing T lymphocytes in AD is due to a reduction in both Th1 and Tc1 IFN-gamma-secreting cells; this may not only contribute to the over-production of IgE, but also explain the high incidence of cutaneous infections observed in AD patients.