CD4⁺ T cells of the cases were fully receptive to HIV super-infection, excluding passive intrinsic resistance to HIV. (A) Purified CD4⁺ T cells derived from the cases (C1, ×; C2, †; C3, ★; C4, ◊), HIV-negative controls (n = 10), typical LTNPs/ECs (n = 11), viremic progressors (n = 10), and Rx<50 (n = 17) were stimulated with medium containing soluble anti-CD3/anti-CD28 monoclonal antibodies and recombinant IL-2 (40 IU/mL) for 3 days, coincubated with magnetized HIV_SF162 in the presence of a super-magnet for 15 minutes, and cultured for 36 hours before analysis for intracellular HIV p24 expression. HIV infection is expressed as the percentage of CD3⁺ lymphocytes expressing p24. Horizontal lines represent median values. Comparisons were made using the Wilcoxon 2-sample test. None of the comparisons was significant. (B) CD4⁺ T cells from a subset of 3 cases (C1, ×; C2, †; C4, ◊), 3 randomly selected LTNPs/ECs, and 3 HIV-negative controls were negatively selected with magnetic beads and subjected to redepletion of CD8⁺ cells. Purity was confirmed to exceed 98% by flow cytometry. After 4-hour incubation with HIV_SF162 at a TCID₅₀ of 2000, cells were washed twice, resuspended in 10% human AB medium not containing human IL-2 at a concentration of 5 × 10⁵ cells/mL, and incubated in 24-well plates at 37°C for 4 days before assessment by flow cytometry for HIV Gag p24 expression and CD8⁺ T-cell overgrowth. HIV infection is expressed as the percentage of CD3⁺ lymphocytes expressing p24.