PDCD1 and pneumonitis: To establish a mouse model of immune-related arthritis and pneumonitis, humanized BALB/c-hPD1/hCTLA4 mice were randomized and injected intraperitoneally with PBS or collagen-specific autoantibodies and LPS, followed by challenging multiple times with vehicle or ICI, leading to the control, CAIA, ICI and CAIA+ICI groups (Figure 1A).