Question

Why do you think neutrophils are not present in the tissues during homeostasis even though they constitutively express the selectins and integrins necessary to enter tissues?

Answer 1

Though the neutrophils constitutively express selectins and integrins, the P-/E-selectin and ICAMS (intercellular adhesion molecules) are only articulated on the vascular endothelium at the locations of inflammation.  

Or it can also be said that while the neutrophil adhesion molecules are constitutively expressed, the vascular endothelial adhesion molecules are induced.