Eosinophilia in premature neonates. Phase 2 of a biphasic granulopoietic response

Eosinophilia within the first 6 weeks of life was studied prospectively in 10 premature neonates. Mean birthweight was 1229 +/- 314 g, and mean gestational age 31.5 +/- 1.8 weeks. Simultaneous changes in eosinophil, neutrophil, total lymphocyte, suppressor and helper T-cell counts and IgE levels were monitored. Infants were designated as responders (eosinophils greater than 1000/microliter for greater than 5 days) and non-responders. In the 6 responders eosinophils increased from 353 +/- 76 (mean +/- SEM) at birth to a peak of 2783 +/- 430/microliter at 20-25 days. Responders had significantly lower neutrophil counts at birth (P less than 0.05), and in 5 of the 6 responders neutrophils increased by more than 100% within 10-15 days; this did not occur in any of the 4 non-responders (P less than 0.025). Lymphocytes and suppressor and helper T cells increased progressively in both groups over the period of study with no differences between responders and non-responders. Birthweight and gestational age were similar in both groups, and there were no apparent causes for the lower neutrophil counts in responders at birth. Eosinophilia was not related to an IgE response. The incidence of eosinophilia in this study is similar to that reported previously, and appears to be part of a biphasic granulopoietic response.