COMPENSATION OF PRELIMINARY BLOOD PHAGOCYTE IMMATURITY IN THE NEWBORNCALF

To estimate the functional maturity of the phagocytic defence in neona tal calves, we analyzed the characteristics of blood phagocytes from c alves (n = 10) 1 h post partum (p.p.) and 4 h p.p. At I h p.p., all ca lves were colostrum-deprived, while 5 calves had received colostrum be fore the 4 h p.p. sampling. The results were compared to those obtaine d from 3-9-week-old calves (n = 10). Phagocytic and oxidative burst ac tivity of polymorphonuclear leukocytes (PMNL) and monocytes were deter mined in whole blood and separately analyzed by flow cytometry. In neo nates prior to colostrum ingestion (1 h p.p.), phagocytic activity of PMNL against non-preopsonized E. coli was lower when compared to PMNL of 3-9-week-old calves. Opsonization of bacteria with pooled plasma fr om adult animals only partially restituted this lower PMNL phagocytic activity, indicating that humoral as well as cellular aspects of PMNL phagocytosis are altered in neonatal calves. In contrast to PMNL, mono cytes of neonates exhibited an enhanced phagocytic activity. The oxida tive burst activity of PMNL, as well as of monocytes was higher in new born calves. During the first 4 h of life, the activities of blood pha gocytes changed. Colostrum ingestion was accompanied by an increase in the percentage of phagocytizing PMNL and monocytes. This increase was absent in colostrum-deprived calves. In contrast, the oxidative burst activity of pha,oocytes decreased with age. In monocytes, the decreas e of oxidative burst activity was only observed in colostrum-fed calve s. In conclusion, some blood phagocyte functions in calves were found to be immature at birth, but these functions are presumably compensate d by high absolute PMNL numbers and by other the more active mechanism s. (C) 1998 Elsevier Science B.V.