Figure 4.

Tax-expressing CD4 ⁺ cells are preferentially killed by CTL when loaded with HLA-A*0201 restricted peptide. Purified CD4⁺ cells from six HLA-A*02⁺ infected individuals (2 AC, 1 P, 3 HAM) were cultured for 12 h alone, to allow expression of viral proteins and any accompanying changes in cellular phenotype. BMLF-1 specific CTLs were introduced to the culture at an E:T ratio of 1:1 with and without the indicated concentration of BMLF-1 peptide. After a further 12 h incubation, the Tax expression by CD4⁺ cells was quantified by intracellular staining and flow cytometry. Percentage specific killing for each population and culture condition was calculated using the baseline frequency of Tax⁺CD4⁺ cells detected in the absence of specific peptide, and absolute CD4⁺ cell counts. Shaded symbols denote the frequency of Tax⁺ cells killed, open symbols denote the frequency of Tax⁻ cells killed for each donor. Statistical analysis was performed using the Wilcoxon matched pairs test, Tax⁺ vs Tax⁻, two-tailed. Bars denote mean ± SEM. See Additional file 6 for donor characteristics.