Flow cytometric analysis of T cell activation. (A) Human PBMCs were incubated for 16 h with Kato III cells at an E/T ratio of 20:1 in the presence of 10 µg/ml DCH, DCH-mu, or cell culture medium (control). CD69 expression on CD8+ T cells was detected by anti-CD69 FITC-conjugated and anti-CD8 PE-conjugated mouse mAb staining. (B) CD69 expression on CD4+ T cells within the PBMC population was detected by anti-CD69 FITC-conjugated and anti-CD4 PE-conjugated mouse mAb staining. (C) Purified human T cells were incubated for 16 h with Kato III cells at an E/T ratio of 10:1 in the presence of 10 µg/ml DCH, DCH-mu, or medium (control). CD69 expression on CD8+ T cells was detected as above. (D) CD69 expression on CD4+ T cells within isolated human T cells was detected as above. Error bars indicate standard deviations from duplicate determinations.