TNFSF13 and rheumatoid arthritis: In RA, there is a significant correlation between increased APRIL levels in the synovium and inflammatory responses. APRIL is found to enhance the survival and proliferation of activated B cells in the inflamed synovial tissue. Expression of TACI and BCMA has been detected in rheumatoid synovial fibroblasts, suggesting that these cells may play an active role in local APRIL signaling, further promoting autoreactive B cell activity.