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

Abstract

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.

Fig. 1

Flow cytometry analysis of CD4 versus IFN-γ (a,b) and CD8 versus IFN-γ (c,d) shows that production of IFN-γ by CD8⁺ (Tc1) cells exceeds production of IFN-γ by CD4⁺ (Th1) cells, both in AD and in control. Peripheral blood mononuclear cells (PBMC) from randomly selected AD patient (a,c) and healthy donor (b,d) were stained using anti-IFN-γ MoAb and FITC-labelled F(ab)₂ goat anti-mouse IgG (abscissa), and subsequently incubated with a PE-conjugated anti-CD4 MoAb (a,b) or anti-CD8 MoAb (c,d) (ordinate), and counterstained for the surface expression of the CD3 marker, using a peridinal chlorophyll protein-conjugated MoAb Leu-4. IFN-γ expression was evaluated on the CD3-gated lymphocyte subpopulation.

Fig. 2

Cytokine mRNA profile of unstimulated peripheral blood mononuclear cells (PBMC) reveals decreased production of IFN-γ, production of IL-4, and increased production of IL-10 in AD patient compared with healthy donor. Cytokine gene expression in PBMC of an AD patient (a,b) and a healthy subject (c,d), unstimulated (a,c) and stimulated for 6 h with phorbol myristate acetate (PMA) and ionomycin (b,d). Reverse transcriptase-polymerase chain reaction (RT-PCR) products were analysed on a 15% agarose gel and detected by ethidium bromide staining. The molecular weight marker used is φX174 DNA HaeIII digest.