Cell surface characterization of T lymphocytes and allergen-specific T cell clones: Correlation of CD26 expression with T-H1 subsets

To evaluate the possibility of using surface molecules as markers for human T helper cell subsets, we studied the expression of surface molecules on T cell clones (TCCs) specific for the major birch pollen allergen, Bet v 1. No difference in the expression of the respective receptors for interferon-gamma (IFN-gamma), IL-4, IL-6, or IL-10 could be detected on T-H subsets, nor did CD25 expression (IL-ZR alpha-chain) differ significantly. However, high expression of CD26 antigen (dipeptidyl peptidase IV) correlated with a T-H1/T-H0-like phenotype, whereas T-H2-like clones displayed a lower expression of CD26 antigen. Comparing cytokine production and CD26 expression simultaneously, we found a correlation between the IL-4/IFN-gamma ratio and the density of CD26 per cell. We could show that the amount of IL-4 secretion, and not of IFN-gamma secretion, was responsible for this correlation. To evaluate whether CD26 antigen expression is regulated by stimuli inducing a T-H1- or T-H2-like phenotype, peripheral blood mononuclear cells (PBMC) were cultured in the presence of IL-4, IFN-gamma, and IL-12, respectively. Incubation with IL-4 led to T cells with a T-H2-like cytokine pattern and a significantly lower expression of CD26; IFN-gamma and IL-12 led to a T-H1 shift associated with an increased expression of CD26 on CD4(+) T cells. By means of intracellular cytokine detection we analyzed expression of CD26 on CD4(+) PBMC stimulated to produce IFN-gamma or IL-4 on a single cell level. All activated, cytokine-producing CD4(+) T cells expressed CD26, but the increase in CD26 expression was higher in cells producing IFN-gamma. These data suggest that regulation of CD26 cell surface expression correlates with the production of T-H1-like cytokines.