PDCD1 and pneumonitis: Through the Mirror-pairing (n = 9) analysis of PD-1 versus PD-L1, it indicated that PD-1 had a much more significant impact on the risk of pneumonitis (OR = 1.46, 95%CI [1.08, 1.98], I2 = 0%, Z = 2.47 (P = 0.01); Fig. S3A) [1, 2, 4, 6–8, 10, 12, 14, 15, 17, 19, 21, 23, 71, 78, 79].