Our cohorts are representative of patients with RA and SLE receiving rituximab in the UK and the salient clinical characteristics (age, gender distribution, disease duration and disease activity scores) of our cohorts are comparable to real-world data of rituximab-treated patients from registries in Europe.51, 52, 53, 54 We provide consistent evidence that FcγRIIIa is the major FcγR associated with both clinical and biological (depth of B-cell depletion) response to rituximab in two autoimmune diseases. This evidence concerns the gene FCGR2A and rheumatoid arthritis.