FIG. 3.

Lack of antigen-nonspecific CD4 T-cell activation. PBMC from pairs of three CMV-positive and three CMV-negative blood donors in all combinations were mixed and stimulated for 6 h using CMV antigen and control antigen. To distinguish cells of the respective donor within the mixture, PBMC of one donor were prestained using FITC-conjugated anti-CD45 antibody (prestained cells are denoted with an asterisk). After stimulation, IFN-γ production was flow-cytometrically analyzed in T cells from each donor in the mixture. (A) PBMC from a CMV-negative (n) and a CMV positive (p) donor were mixed (*p/p, *n/n, *p/n; 10⁶ PBMC from each donor) and stimulated. (B) PBMC from three CMV-positive (prestained) and three CMV-negative donors were mixed in all possible combinations (n = 9; *CMV+/CMV−). Six different combinations of PBMC from CMV-negative (*CMV−/CMV−) and CMV positive donors (*CMV+/CMV+) were stimulated as controls.