Leukocyte adhesion and extravasation were defective in TNF-α–treated cremaster muscle of HPK1-deficient mice. Intravital microscopy (A-C) of postcapillary venules in mouse cremaster muscle 2.5 hours after intrascrotal injection of TNF-α (500 ng). (A) Leukocyte rolling flux fraction, (B) rolling velocity, and (C) leukocyte adhesion efficiency were analyzed offline. n = 32 venules from 5 HPK1^+/+ mice and 32 venules from 4 HPK1^−/− mice; accumulated frequency of rolling velocity includes 259 cells from 5 HPK1^+/+ mice and 275 cells from 4 HPK1^−/− mice. Number of (D) intravascular and (E) perivascular leukocytes as quantified in Giemsa-stained cremaster muscle whole mounts of HPK1^+/+ and HPK1^−/− mice. Cremaster muscles were fixed and stained 2.5 hours after intrascrotal injection of TNF-α (500 ng), and the number of leukocytes was assessed histologically. n = 50 venules from 3 HPK1^+/+ mice and 48 venules from 3 HPK1^−/− mice. (A-E) Diagrams show mean ± SEM; *P < .05; **P < .001; n.s. = not significant.