Relationship Between T LYmphocytes Depletion and Clinical Response to RITUXimab in Rheumatoid Arthritis (LYRITUX)

Rituximab, an anti CD-20 monoclonal antibody targeting B lymphocytes is prescribed in rheumatoid arthritis (RA) patients refractory to TNF alpha antagonists. According to previous studies, (Edwards, Szczepanski et al. 2004; Cohen, Emery et al. 2006; Emery, Fleischmann et al. 2006) 25 to 50% of patients have an insufficient or absence of response to rituximab at week 24. In the pathogenesis of RA, B and T lymphocytes are tightly linked through the APC fonction and cytokines production of B lymphocytes. At present, a white blood cells count is recommended in routine every 3 months in patients receiving rituximab, since cases of neutropenia have been observed in approximately 8% of patients with lymphoma after treatment. In RA patients, B lymphocytes count before each rituximab course should be done to prevent opportunistic infections (Pham, Fautrel et al. 2008).

In a recent retrospective study, a CD4+ T-lymphocytes depletion was observed after a first course of rituximab in RA patients. The absolute CD4+ number at week 12 was 37% (±33) of the baseline value, leading to < 200 cells/µL in 5% of patients. Interestingly the absence of CD4+ T-lymphocytes depletion was observed in clinical non-responders, suggesting the involvement of T-lymphocytes in the mechanism of action of rituximab (Mélet, Mulleman et al. 2013). Moreover, few case reports of RA patients developing opportunist infections in conjunction with CD4+ T-lymphocyte depletion have been published (Teichmann, Woenckhaus et al. 2008; Clifford, Ances et al. 2011). So far no prospective study have supported the usefulness of lymphocyte phenotyping, in particular T-lymphocytes, to monitor rituximab-treated RA patients.