Irreversible neutrophil aggregation. A mechanism of decreased newborn neutrophil chemotactic response

To investigate the neutrophil-neutrophil interactions of the newborn for possible clues to the etiology of decreased newborn neutrophil (PMN) chemotaxis, the authors compared adult and newborn C5a-induced PMN aggregation and chemotaxis at various PMN concentrations. Using Craddock's technique of C5a-induced aggregation, the authors found that the newborn lacks the normal biphasic aggregation-deaggregation seen in the adult, suggesting irreversible aggregation similar to that seen when adult PMNs are pretreated with cytochalasin B. Chemotaxis of adult and newborn PMNs was studied with a modified Gallin radiolabel technique. A linear correlation between PMN concentration and corrected chemotatic response was found with both adult (r²=0.93) and newborn (r²=0.90) PMNs in the range 0.1 x 10⁶ to 20 x 10⁶ PMNs/ml. Random migration was not augmented by increased PMN concentration. The augmentation of newborn PMN chemotaxis was less than that of the adult (adult slope = 2426; newborn slope = 983). Irreversible newborn PMN aggregation may be the underlying event producing decreased PMN chemotaxis and interfering with the normal chemotactic augmentation caused by increased PMN concentration.