FIG. 2.   Total HIV-specific CD4⁺ (A) and CD8⁺ (B) T-cell responses in samples from 23 untreated HIV-infected patients. PBMC isolated from patients 1 to 23 (see Table 1) were incubated with peptide mixtures containing 15-mers overlapping by 11 amino acids derived from HIV Gag, Pol, Env, Nef, Tat, Rev, Vif, Vpr, and Vpu in the presence of costimulatory antibodies as described in Materials and Methods. The bars in panel A represent the percentage of CD3⁺CD8CD69⁺ IFN-⁺ cells that responded to each peptide mixture with background (CD28-CD49d alone) IFN- production from the CD3⁺CD8⁺ population removed. The bars in panel B represent the percent of CD3⁺CD8⁺CD69⁺ IFN-⁺ cells that responded to each peptide mixture with background IFN- production removed. Background IFN- production from CD3⁺CD8⁺ cells was 0.1% in all patients except for patients 15 (0.15%), 17 (0.37%), and 22 (0.2%). Background IFN- production in CD3⁺CD8 cells was 0.1% in all patients except for patients 10 (0.16%), 15 (0.16%), and 21 (0.17%).