Effects of single-domain antibody A1 on implanted synovium and cartilage erosion in SCID-HuRAg mice. Rheumatoid arthritis (RA) synovium with normal human articular cartilage was co-implanted under the back muscle chamber of SCID-HuRAg mice. After 4 weeks of treatment, the co-implants were taken and stained with hematoxylin and eosin, and were evaluated histologically under a microscope. (A) Representative image of implanted synovium in SCID-HuRAg mice in each treatment group (n = 6 per group) (magnification × 400). (B) Statistical results of the numbers of inflammatory cells in each treatment group. (C) Representative images of human cartilage erosion in SCID-HuRAg mice of different groups (magnification × 200). (D) Cartilage erosion score after treatment in each group. Black arrows, invasive front of the synovial tissue. c, cartilage. *P <0.05 versus control antibody group. PBS, phosphate-buffered saline; sdAb, single-domain antibody.