Staphylococcus aureus skin colonization in atopic dermatitis children is associated with decreased IFN-γ production by peripheral blood CD4+ and CD8+ T cells

Atopic dermatitis (AD) is a chronic inflammatory skin disorder, which is associated with an increased expression of Th2 cytokines with concomitant decrease in IFN-gamma production by circulating CD4(+) and CD8(+) T cells. The skin of patients with AD is often colonized by Staphylococcus aureus, which may reflect in changes in immunological parameters. The aim of the study was flow cytometric measurement of some peripheral blood lymphocyte subsets expressing naive/memory marker (RA/RO) and activation marker (CD25) as well as intracellular production of IFN-gamma by peripheral blood CD4(+) and CD8(+) T cells from varied severity AD children and determine the impact of S. aureus skin colonization on cytokines profiles. There was a significant increase in the percentage of CD4(+) and CD8(+) T cells producing IL-4 and IL-13 and decrease in the percentage of CD4(+) and CD8(+) T cells producing IFN-gamma upon in vitro stimulation with phorbol 12-myristate 13-acetate and ionomycin in children with AD compared to healthy ones. The absolute number of CD4(+) and CD8(+) T cells expressing memory marker CD45RO was elevated as compared with controls. The severity of AD was positively correlated with the percentage of lymphocyte subsets: CD45RO(+), CD4(+)CD45RO(+), and the percentage of CD3(+) and CD4(+) expressing CD25 as well as the number of S. aureus on the skin. In conclusion, both CD4(+) and CD8(+) memory T cells are involved in the immunopathogenesis of AD. S. aureus skin colonization is related with disease severity and changes in expression of CD45RO and CD25 on T cells. A decrease in the percentage of CD4(+) and CD8(+) T cells producing IFN-gamma in AD children may explain propensity for skin infection.