Effects of age on CD4 upregulation in p146-162-responsive Vβ6+CD4+ T cells. Young (2-4 months of age) and old (20-23 months of age) transgenic and nontransgenic mice were immunized with p146-162; draining lymph nodes were extracted and expanded in vitro with the immunizing peptide. The LNCs were stained to detect CD4, CD25, and Vβ6 using antibodies conjugated to FITC, APC, and PE, respectively. The cells were analyzed by FACS to determine whether CD4 had been upregulated in the Vβ6+ population. The experiment was then repeated with an equivalent number of mice of the same age groups. Representative dot plots are shown (Panel A). The frequency of Vβ6+CD4high T cells within the lymphocyte population is shown for the individual mice from the combined experiments (Panel B). The solid line represents the mean value within each group.