Deformability of passive and activated neutrophils in children with Gram-negative septicemia.

Animal experiments suggest that obstruction of small vessels by polymorphonuclear neutrophils (PMNs) may contribute to the disturbed microcirculation in septic shock. The purpose of this investigation was to study deformability and volume of passive and activated PMNs and immature neutrophils in 15 children with Gram-negative septicemia and in 20 healthy children. Membrane cytoplasm tongues of neutrophils were aspirated by means of a micropipette system into 2.5-microm (diameter) pipettes for 60 s. Tongue growth was used as an indicator of deformability and the cell volume was calculated from the cell circumference before aspiration. Septicemic children showed higher percentages of immature neutrophils (38+/-13%) and activated PMN (12+/-5%) than healthy children (3+/-2% and 3+/-2%). In septicemic children, cellular volume of passive neutrophils decreased progressively with increasing maturity from myeloblasts (493+/-105 fL) to mature PMNs (346+/-29 fL) and the final tongue length in the micropipette increased from 2.7+/-1.1 to 8.5+/-1.8 microm during maturation. The final tongue length of activated PMNs was decreased by 60% compared with that of passive PMNs. The increased number of rigid activated and immature neutrophils may contribute to impaired microcirculation in septicemic patients.