CD4, CCR5, and CXCR4 expression in CD4⁺ T-cell lines established from pediatric and adult donors. (A) T-cell lines were stained with anti-CD4–FITC, anti-CCR5–PE, and anti-CXCR4–PE mAb at the time of viral infection, and the percentage of positive cells was detected by cytofluorimetric analysis. The results from a single experiment on pediatric and adult cell lines representative of 6 and 5 different donors, respectively, are shown. No significant differences were seen between child and adult cell lines. (B) Percentage of CD4⁺ cells (mean ± SEM of 6 independent experiments made in quintuplicate) expressing CCR5 or CXCR4 in child and adult cell lines is reported without showing any significant difference. (C) T-cell activation marker expression of pediatric and adult CD4⁺ T-cell lines indicates no significant differences (one experiment representative of 6 pediatric and 5 adult cell lines is shown). (D) Mean expression levels of activation markers expressed by CD4⁺ T-cell lines are shown (n = 6 pediatric and 5 adult cell lines). (E) Proliferation of pediatric and adult CD4⁺ T-cell lines was assessed by the MTT assay at the time of infection. Mean ± SEM values of the proliferation (n = 6 pediatric and 5 adult cell lines) are shown and do not indicate differences in child versus adult cell lines.