Background: Rituximab is a chimeric IgG1 kappa immunoglobulin that has been genetically modified to incorporate human constant region sequences together with murine light- and heavy-chain variable region sequences. People use it to treat rheumatoid arthritis and certain malignancies. Objective: The study aimed to assess the potential association between the serum levels of Factor I, CD59, interleukins (IL)-6, and interferon-gamma (IFN)-γ and the response to Rituximab treatment in Iraqi rheumatoid arthritis patients. Methods: A cross-sectional study was conducted at the rheumatology center at Baghdad Teaching Hospital. Ninety adult patients who have been diagnosed with rheumatoid arthritis and are receiving Rituximab intravenous infusions were included. The enrolled patients were divided into a responder group (45 patients) and a non-responder group (45 patients). The response to Rituximab was assessed according to the 28-joint Disease Activity Score (DAS28). Results: The serum levels of Factor I and CD59 were significantly higher in the non-responders group in comparison to the responders group. In addition, the serum IL-6 and IFN-γ levels were significantly elevated in the non-responders group in comparison to the responders group. The estimated marker serum levels showed a strong, significant correlation with the 6-month change in DAS28. Conclusions: In Rituximab nonresponder RA patients, serum levels of Factor I, CD59, Factor H, IL-6, and IFN-γ are higher, and they have good potential to be used in the assessment of the response to Rituximab therapy.
