PDCD1 and arthritic joint disease: To determine the importance of TNF-α in the pathogenesis of severe arthritis and pneumonitis, humanized BALB/c-hPD1/hCTLA4 mice were randomized and injected intraperitoneally with vehicle as to the control or collagen-specific antibody and LPS, followed by injecting with ICI as the CAIA+ICI (Figure 3A).