DIFFERENT EXPRESSION AND MOBILIZATION OF THE COMPLEMENT REGULATORY PROTEINS CD35, CD55 AND CD59 IN NEONATAL AND ADULT NEUTROPHILS

We investigated the expression and the N-formyl-methionylphenylalanine (fMLP)- and interleukin-8 (IL-8)-induced mobilisation of the compleme nt regulatory proteins CR I (CD35), decay-accelerating factor (CD55) a nd CD59 on neutrophils in neonates and adults. The expression of CD35 on resting neonatal neutrophils was significantly higher than in adult s. Both fMLP and IL-8 increased CD35 expression more markedly in adult s. CD55 on resting neutrophils in neonates was significantly higher th an in adults, but did not further increase upon fMLP stimulation as op posed to adults, The increase in CD59 expression was more pronounced i n adult neutrophils and was significantly higher than in neonates afte r fMLP activation. The addition of the protease inhibitor phenylmethan esulphonyl fluoride during fMLP activation improved the upregulation o f CD35 significantly more in neonates, but not CD55 or CD59. This effe ct could be replaced by human normal sera. These data demonstrate that differences exist between neonatal and adult neutrophils with respect to the expression and mobilisation of functional receptors related to protection from autologous complement lysis and may indicate differen ces in the efficiency to circumvent complement-mediated cell damage at the inflammatory site.