Abstract 116

Background. In the neonatal period the adhesion of WBC to the vascular endothelium and the respiratory burst and SR production during the inflammatory process are reduced compared to the adult. These deficits are implicated in the higher susceptibility of the newborn to infections.β21 receptors play an important role in the inflammatory response to infection, since they are involved both in the adhesion process and oxidative metabolism of WBC. Aims. To study the expression ofβ2I in Lymphocytes, Monocytes and Neutrophils (PMN) of preterm (PT) and Term (T) Newborns (N) and their relationship with Gestational Age (GA, w), Postnatal Age (PNA, d.) and Type of Delivery(Vaginal Delivery, VD; Cesarean Section, CS). To study the SR production in PMN of the same neonates. To study the reciprocal and interdipendent activation between "respiratory burst" and β21 (CD11/CD18) receptors in neonatal WBC. Materials. Samples of cord blood at birth and venous blood at 3 d PNA from 11 TN delivered by VD, 12 TN delivered by CS and 12 PTN (GA: 32-37 w) delivered by CS were compared with venous blood from 40 normal adult controls. Methods. Cytofluorimetry (direct and indirect immunofluorescence) for β2I expression. Spectrophotometric assay (c Fe3+ Cytocrome) for RS production, both without stimulation and following stimulation with Zymosan (ZS) and Opsonized Zymosan(OZS). Results. The % of Lymphocytes, Monocytes and Neutrophils expressing β2I in all 3 groups of neonates were significatively lower than in adult controls. This was particularly true for CD11b and CD11c in lymphocytes, which decreased further from birth to 3 d PNA. The type of delivery and GA did not seem to influence significatively β2I expression. Neutrophil's basal RS production was low compared to adult controls and even lower with ZS stimulation. Furthermore RS production was higher at birth than at 3 d. PNA (particularly so for VD). These patterns were partially corrected by OZS stimulation. Conclusions. Our results suggest a reduced β2I expression in WBC of newborn infants, which could contribute to the deficient adhesion capability of leucocytes described in the newborn. The delivery process (VD and CS) and GA (in the range of our study, 32-41 w) did not seem to influence this pattern. The reduced expression of β2I in leucocytes could also be responsible for the lower production of SR after stimulation with Zymosan, since this substance utilizes β2I to enter the cells and stimulate the respiratory burst.

(Supported in part by a Grant of the Italian Ministry of Health).