E-selectin–mediated slow rolling in vivo requires PSGL-1 and CD44, all 3 SFKs, and Btk. (A) Velocities of leukocytes rolling in TNF-α–stimulated venules of mice of the indicated genotypes, measured before and after injecting a blocking mAb to P-selectin and then a blocking mAb to β2-integrins. (B-D) Velocities of PKH26- and PKH67-labeled leukocytes of the indicated genotypes in the same TNF-α–stimulated venules. The labeled cells were pretreated with PTx, and the mice were pretreated with anti–P-selectin mAb. (E) Lethally irradiated WT mice were injected with WT LysM-GFP⁺ bone marrow cells mixed with an equal number of GFP-negative WT or Btk^−/− cells. After 8 weeks, the mice were treated with PTx and anti–P-selectin mAb, and rolling velocities of GFP-positive and GFP-negative leukocytes were measured in the same TNF-α–stimulated venules. The data represent the mean ± SEM from at least 3 experiments. *P < .01.