HIV-1 resistance in CEM.NKR subpopulations. A) HIV-1 (NL4-3) replication in CEM.NKR and CEM-T4 cells over a 16-day period. B) HIV-1 replication in cell clones from CEM.NKR. CEM.NKR cells were subjected to limiting dilution and eight cell clones (#1 to #8) were isolated. Together with CEM-T4 and the parental CEM.NKR, these clones were infected with HIV-1 (NL4-3) and viral production was measured for 32 days. C) CD4 and CXCR4 surface expression in cell clones from CEM.NKR. The parental or each individual cell clone was stained with fluorescence-conjugated antibodies (CD4-FITC, CXCR4-PE) and analyzed by flow cytometry.