Do regulatory T cells contribute to Th1 skewness in obesity?

Background: Recent data suggest that an increased prevalence of interferon-gamma (IFN-gamma) producing CD4(+) cells is present in obesity. Regulatory T cells (Tregs) have a strong impact on activation and proliferation of CD4(+) lymphocytes. Data are not available about Tregs and their possible contribution to chronic mild inflammation in obesity. Design: We investigated the prevalence of Tregs in obese children. We also collected data about dendritic cells and monocytes (so-called antigen presenting cells, APCs), important modulators of Tregs and we determined the cytokine production of CD4(+) lymphocytes, the main target cells of Tregs. Methods: Twelve obese children and 10 healthy age-matched controls have been enrolled. For flow cytometric analyses, peripheral blood mononuclear cells were used. We determined the prevalence of Tregs by Foxp3 expression of CD4(+) cells; prevalence of myeloid and plasmacytoid dendritic cells (DCs); prevalence of tumor necrosis factor (TNF)-alpha and interleukin(IL)-12 producing monocytes; and prevalence of IL-2, IL4 and IFN-gamma producing CD4(+) cells. Results: The prevalence of Tregs, DCs, TNF-alpha and IL-12 producing macrophages, IL-2 and IFN-alpha producing CD4(+) cells was similar in both groups. The prevalence of IL-4 producing CD4(+) cells was lower in obese children than in healthy controls (p=0.028). The ratio of IFN-gamma(+)/ IL-4(+) CD4(+) cells was higher in obese children than in those with normal weight (p = 0.046). Conclusions: CD4(+) reactions are polarized toward Th1 direction in obesity. The unaltered number of Treg and APCs suggests that these immune regulator cells do not contribute to altered immune status in obese children.