The A120 mAb-treatment induces the production of CCR5 binding β-chemokines and the down-modulation of CCR5 expression. PBMCs from 6 donors were activated with anti-CD3/28 mAbs for 1 day, washed, aliquoted and then incubated in the presence of 10 μg/ml A120 mAb or isotype control mAb for an additional day. (a) Changes in the concentrations of MIP-1α, MIP-1β and RANTES in the culture supernatants were assayed by ELISA. (b and c) Cells were analyzed for changes in the cell surface expression of CCR5 and CXCR4 on gated populations of CD4+T cells (MFI denotes mean fluorescence intensity). A representative flow cytometry dot blot profile is shown.