VSIR and neoplasm: We found that the tumor growth was significantly inhibited by myeloid cell–specific genetic deletion of PD-1H, compared with littermate controls (mean radiance in LysM-Cre+PD-1Hfl/fl versus LysM-Cre–PD-1Hfl/fl on day 23: 1.7 × 109 versus 1.7 × 106, n = 9, P = 0.03) (Figure 3C).