Division of T-cell populations defined by their CD57 and CD28 expression patterns.

PBMCs from a healthy individual were stained with anti–CD57 FITC, anti–CD28 PE, anti–CD8 PerCp, and anti–CD45RA APC. Panel A shows the CD57 (x-axis) versus CD28 (y-axis) staining pattern of memory CD8⁺ T cells with CD45RA⁺CD28⁺events removed to examine the memory CD8⁺ T cells. The numbers represent the percentages of CD28⁺CD57⁻, CD28⁺CD57⁺, CD28⁻CD57⁺, and CD28⁻CD57⁻ populations. (B) PBMCs were CFSE labeled and stimulated with SEB for 4 days. Following stimulation, PBMCs were stained with CD57 PE, CD8 PerCP, and CD28 APC. CFSE histograms are demonstrated representing the CD28⁺CD57⁻ population (upper left histogram), CD28⁺CD57⁺ population (upper right histogram), CD28⁻CD57⁻ population (lower left histogram), and CD28⁻CD57⁺ population (lower right histogram). The numbers indicate the percentages of each population that had divided (calculated using the proliferation platform of FlowJo). These data are representative of experiments conducted on PBMCs from 6 separate individuals and using SEB, anti-CD3, or phytohemagglutinin as the stimulus (C). Wilcoxon matched pairs test demonstrated that the CD28⁻CD57⁻CD8⁺ T-cell populations contain significantly more proliferation-competent T cells compared with either CD57⁺CD8⁺ T-cell population (P = .004). Vertical bars represent the 25th to 75th percentiles.