PDCD1LG2 and systemic lupus erythematosus: As shown in Fig. 7, SLE patients have significant elevated serum levels of soluble PD-1, PDL-2 and TIM3 than HCs (sPD-1: 396.2 ± 69.71, N = 77 vs. 111.1 ± 32.92, N = 92 p = 0.0001; sPDL2: 16.97 ± 0.9238, N = 87 vs 12.78 ± 0.2314, N = 92 p < 0.0001; sTIM3: 6.822 ± 1.5367, N = 91 vs 3.675 ± 0.08441, N = 92 p < 0.0001).