Peripheral blood T4 cell surface CCR5 density as a marker of activity in rheumatoid arthritis treated with anti-CD20 monoclonal antibody.

The chemokine (C-C motif) receptor CCR5 and its ligand CCL5 play key roles in the intra-articular recruitment of peripheral blood mononuclear cells (PBMC) in rheumatoid arthritis (RA). Therefore, using quantitative cytofluorometry, we followed T4 cell surface CCR5 density in 27 subjects with RA before and after treatment with the anti-CD20 monoclonal antibody rituximab. We observed low T4 cell surface CCR5 densities before treatment, which correlated positively with disease activity, as determined using a disease activity score evaluated on 28 joints (DAS 28), and negatively with CCL5 mRNA concentrations in PBMC, contrasting with a high proportion of intracellular CCR5 molecules, a pattern compatible with ligand-induced CCR5 internalization. At 3 months post-treatment, CCL5 mRNA expression in PBMC declined, whereas T4 cell surface CCR5 densities increased proportionally to the decrease in DAS 28. Thus, peripheral blood T4 cell surface CCR5 density is a good surrogate marker of RA activity and of the efficiency of anti-CD20 therapy.