Polyfunctional profile of CD4⁺ T cells.

<p>PBMCs isolated 2 weeks after the fourth immunization were stimulated <i>in vitro</i> with a SIVpol peptide pool mix for 5 hours. Cells were stained for intracellular production of IFN-γ, TNF-α and IL-2 and degranulation by CD107a. The magnitude of the SIVgag (white), env (grey) and pol (black) responses are shown as stacked means ± SEM for each group (<b>a</b>). The percentage of the total functional response that has a CD28⁻CD95⁺ (black bar) or CD28⁺CD95⁺ (white bar) is shown as group means ± SEM (<b>b</b>). Pie charts show the proportion of antigen-specific CD4⁺ T cells that have 4 functions (purple), 3 functions (yellow), 2 functions (green) or 1 function (light blue) (<b>c</b>). The bar graphs depict the absolute frequency of each of the 15 functional combinations for the DNA (red), 4-1BB (blue), CTLA-4 (orange), Combo (green) and Saline (black) groups in response to SIVgag, env, and pol after background subtraction (<b>d</b>).