When using the Mirror-pairing for comparing PD-1 with PD-L1, the risk of pneumonitis caused by PD-1 was significantly higher than that of the PD-L1 group (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], which the difference was statistically significant. The gene discussed is PDCD1; the disease is pneumonitis.