Subset III cells.

Subset III cells differ from subset I and II cells in the expression of memory markers and have a high intracellular granzyme B content. Each subset of CD8⁺ T cells was analyzed for cell surface levels of 4-1BB, CD45RO, CCR6, and intracellular granzyme B by 3-color staining along with staining for CD28 and CD8 expression. Expression of markers in each gated subset of cells (I, II, and III) is displayed by the filled histograms. Open histograms represent the cells stained with the isotype control Ab. The percentages represent the CD8⁺ T cells positive for each marker. The cell size of each subset was assessed by the forward scatter (FSC) intensity; these particular numbers represent the mean intensity of FSC as a parameter for cell size. The results in this figure are representative of 4 experiments.