(a) Schematic representation of kinetics experiment: the cells were pretreated for 1 h with cycloheximide (CHX) and then incubated, or not, with CCR5 Ab Pos and CCR5 Ab Neg. The cells were harvested at t0 (corresponding to 30′ of CCR5 modulating factors incubation, washing and additional 120′ of cells incubation in medium without stimuli (150′)), t1 (corresponding to 48 h of factors incubation), t2 (corresponding to 48 h of factors incubation, washing and a further 24 h of cells incubation in medium without stimuli) and t3 (corresponding to 48 h of factors incubation, washing and a further 72 h of cells incubation in medium without stimuli). (b) Real time RT-PCR analysis of β-arrestin1 (β1) and β-arrestin2 (β2), in R5-SupT1-L23 cell line treated with the CHX inhibitor and stimulated with CCR5 Ab Pos and the appropriate control, compared to the untreated cells, at t2. (c) Real time RT-PCR analysis of β-arrestin1 (β1) and β-arrestin2 (β2), in CD4+ T lymphocytes treated with the CHX inhibitor and stimulated with CCR5 Ab Pos and the appropriate control, compared to the untreated cells, at t3. Bar graphs represented mean ± SD of three independent experiments. Student’s t-test was performed and p values are shown. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001.