Fig 3.

Flow cytometric analysis of cells responding to HCV peptide antigens demonstrates that both CD4⁺ and CD4⁻ T cells produced IFN-γ in seronegative aviremic health care workers. PBMC were stimulated with 15-mer HCV peptide antigens, and the cells were harvested for flow cytometric analysis by intracellular staining for IFN-γ as described in Materials and Methods. Data were analyzed using FlowJo software (Tree Star Inc., CA). The cells were gated on small lymphocytes using side and forward light scatter profiles and then on CD3⁺ T cells (not shown). (A) Example of the synthesis of IFN-γ by CD4⁺ and CD4⁻ T cells in the presence of medium (DMSO control), a responding HCV antigen pool (I), and a nonresponding pool (M) as shown in the panel from left to right, respectively. (B) Cumulative percentage of CD4⁺ and CD4⁻ T cells producing IFN-γ in response to HCV antigen pools F (left) and I (right) among responding (n = 7) and nonresponding (n = 6) health care workers, respectively. Error bars represent SEM.