Unexpectedly, PS expression on platelets (or leukocytes) did not increase significantly with acute exposure to LPS. PS is expressed in the inner leaflet of plasma membrane but rapidly inverts to outer surface following activating stimuli [48, 49, 50] . Exposure of PS to the outer membrane surface also occurs with release of MV [51] . Results of the present study are consistent with reports that production of MV is not accompanied by PS expression on cell of origin but might be restricted to that portion of the membrane undergoing MV blebbing [52] .