Distributions of CD4, Th1, and Th2 in adults (n = 16; A) and children (n = 50; B). Distributions of CD4, Th1, and Th2 in adults (n = 16; A) and children (n = 50; B). Whole blood samples collected from adults and children were stimulated with PMA and ionomycin in the presence of brefeldin A for 4 hours at 37°C and stained with monoclonal antibodies specific for the CD4 surface antigen and intracellular IFN-γ/IL-4 cytokines, with IFN-γ and IL-4 serving as the signature cytokines of Th1 and Th2 cells, respectively. Paurene Duramad et al. Cancer Epidemiol Biomarkers Prev 2004;13:1452-1458 ©2004 by American Association for Cancer Research