Cooperative PSGL-1 and CXCR signaling in neutrophils promotes DVT. In flow-restricted IVCs, neutrophils rolling on P-selectin signal through PSGL-1, in part through phosphorylation of tyrosine 145 on SLP-76. Rolling neutrophils signal through CXCR2 after engaging CXCL1 immobilized on proteoglycans. These signals cooperatively activate integrin αLβ2, which causes neutrophils to decelerate and arrest on ICAM-1. Cooperative signaling in adherent neutrophils triggers release of procoagulant NETs. See “Discussion” for details.