Ability of HIV-1–infected CD4⁺ T cells and HIV-1–infected macrophages to stimulate cytokine production by HIV-1–specific CTLs. Cultured CD4⁺ T cells and macrophages were infected with JRFL_{NL-432 Nef} or JRFL_{NL-M20A Nef}. JRFL_{NL-432 Nef-}infected macrophages (22.7% p24 antigen-positive) and CD4⁺ T cells (19.9% p24 antigen-positive), as well as JRFL_{NL-M20A Nef-}infected macrophages (21.5% p24 antigen-positive) and CD4⁺ T cells (22.4% p24 antigen-positive) were used to stimulate 3 HLA-B*5101-restricted CTL clones at an effector-stimulator (E/S) ratio of 1:4. (A) The frequency of cells expressing each cytokine is shown as a percentage of the total number of CD8⁺ cells. (B) The frequency of cells expressing these cytokines among total cytokine-producing cells is also shown in this pie chart.