As revealed by the intensity of labeling, both TG2 and cross-linking activity were detectable at day 18 after the induction of arthritis and increased progressively in the synovial membrane and adjacent cartilage of CIA rats, except at day 32, when the intensity of TG2 labeling declined (Figure 1A and Additional file 1, Figure S1). The gene discussed is TGM2; the disease is arthritic joint disease.