Critical analysis of rituximab-induced serological changes in connective tissue diseases

A survey of PUBMED and EMBASE supplied 21 articles dealing with the effect of rituximab (RTX) on immunoglobulin (Ig) and autoantibodies (Abs) in nonorgan-systemic autoimmune diseases, and another 12 articles were found by hand search. No statistics could be performed due to the lack of numerical data in the articles. RTX tended to diminish total Ig but still within the normal ranges, more for IgM than IgG and IgA. Rheumatoid factor level decreased by 30 to 60% 3-6 months after RTX, whereas anti-cyclic citrullinated peptide Ab titers declined modestly. In contrast, anti-DNA and anti-C1q Ab levels showed a marked decrease, whereas the other anti-extractable nuclear antigens Ab (anti-SSA, SSB, SM, RNP...) were stable. There are claims for an increase in the BAFF level by approximately 2.5 to 3-fold at 3-4 months, and a return to pre-treatment value at 8-12 months. RTX-induced changes in the serum bring about new insights into mechanisms of action. Therefore, more attention should be paid to such parameters in clinical trials.