Effects of rituximab therapy on B cell differentiation and depletion

Rituximab is a human/murine chimeric anti-CD20 monoclonal antibody. It is largely used to treat B cell malignancies and has become standard in the management of B cell‑mediated diseases such as rheumatoid arthritis and granulomatosis with polyangitis. The effects of rituximab need to be monitored by B cell phenotyping. Evaluate possible surface markers for monitoring B cell development in response to rituximab treatment. This review discusses the literature on the B cell surface markers analysed by flow cytometry in patients treated with rituximab. A panel of biomarkers of response to treatment to monitor by flow cytometry is also suggested. B cell phenotyping is useful to predict clinical relapses after rituximab treatment. The proposed panel of biomarkers includes CD38⁺⁺CD24⁺⁺IgD^+/- immature B cells and IgD^-CD38^+/- memory B cells. In responders, Th1/Th2 balance and tolerance cells (CD4⁺CD25⁺CD127^-/low Treg cells and CD19⁺CD24^hiCD38^hi Breg cells) tend to be restored after rituximab therapy. Furthermore, in responder patients, indirect depletion of CD19^+/-CD27⁺⁺CD38⁺⁺ preplasma cells can be proposed as a predictor of response. Flow cytometric analysis of samples from patients treated with rituximab is a useful strategy to stratify patients according to response to treatment. Identification of B cell differentiation stages by means of a specific flow cytometry panel could improve monitoring of rituximab effects and enable non-responders to be distinguished from good responders.