Inefficient in vivo neutrophil migration in neonatal rats.

While neutrophils from neonates respond less efficiently in vitro to a chemotactic stimulus than do adult cells, the in vivo recruitment of phagocytic cells to focal sites of inflammation in some situations appears to be similar in adults and neonates. To resolve this apparent discrepancy between the in vitro and in vivo observations, neonatal and adult rats were inoculated intraperitoneally with a variety of chemotactic agents. The neutrophil response was far more intense in adults than in neonates, strengthening the hypothesis that chemotaxis is less efficient in neonates than in adults. This relative deficiency may play an important role in the inability of the newborn to deal with infection effectively.