  We have characterized the two-dimensional spatial dependence of the
hydrodynamic interactions between two adhesively rolling leukocytes in a live
venule in the mouse cremaster muscle. Two rolling leukocytes were observed to
slow each other down when rolling together in close proximity, due to mutual
sheltering from the external blood flow in the vessel lumen. These results are
in agreement with a previous study of leukocyte rolling interactions using
carbohydrate-coated beads in a parallel-plate flow chamber and a detailed
computer model of adhesion in a multicellular environment.
