By performing RT-PCR for Iγ-Cμ circular transcripts, which are transiently produced for around 48 h following class switching from IgM to IgG [50], we demonstrated (Figure 6A) their invariable detection in those RA transplants also expressing AID and CD21L mRNA, confirming the functionality of AID expression in synovial grafts. Here, AICDA is linked to rheumatoid arthritis.