Activation and division of γδ T cells in response to ESAT-6. (A,B) Activation of γδ T cells induced by ESAT-6. PBMCs were cultured in the presence or absence of ESAT-6 and ESAT-6 plus anti-CD28. After stimulation for 72 hours, cells were harvested and stained for CD25 and CD69. γδ T cells were gated and analyzed for CD25 (A) and CD69 (B) expression. (C) Mean value of CD25 and CD69 expression on γδ T cells from 3 separate experiments was shown. (D) Division of γδ T cells induced by ESAT-6. Purified γδ T cells were labeled with CFSE (5μM) and cultured with or without ESAT-6 at the concentration of 5 and 10 μg/mL plus anti-CD28 for 6 days. CFSE-labeled cells were gated for FACS analysis. The percentages of divided cells in each condition were analyzed. Data are representative of 2 separate experiments with similar results.