Mode of delivery directs the phagocyte functions of infants for the first 6 months of life

Factors that direct the immune responsiveness of the newborn beyond the imm ediate post-natal period are not known. We investigated the influence of mo de of delivery and type of feeding on the phagocyte activity during the fir st 6 months of life. Sixty-four healthy infants (34 delivered vaginally and 30 by elective Caesarean section) were studied at birth and at the ages of 2 and 6 months. Phagocyte functions were studied by measuring the chemilum inescence (CL) activity of whole blood and isolated leucocytes and by inves tigating the expression of phagocyte receptors (Fc gamma RI (CD64), Fc gamm a RII (CD32), Fc gamma RIII (CD16), CR1 (CD35), CR3 (CD11b) and Fc alpha R (CD89)) on neutrophils, monocytes and eosinophils by using receptor-specifi c MoAbs and immunofluorescence flow cytometry. Infants born by elective Cae sarean section had significantly higher CL activity than those delivered va ginally during the entire 6-month follow up. In addition, infants who recei ved formula feeds had significantly higher CL activity at 6 months of age a nd higher expression of Fc gamma RI-, Fc alpha- and CR3-receptors on neutro phils than infants exclusively breast-fed. We suggest that stress reaction associated with labour influences the phagocytic activity measured in the c ord blood but later during infancy the intraluminal antigens, gut microflor a and diet, become important determinants in immune programming of human in dividuals.