CD40LG and rheumatoid arthritis: 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.