LYMPHOCYTE SUBPOPULATIONS IN HEALTHY 1-3-DAY-OLD INFANTS

The primary objective of this study was to establish reference ranges for the major (B, T, and natural killer; NK) and clinically relevant m inor lymphocyte subsets in the peripheral blood of healthy 1-3-day-old infants and then to compare the results with those obtained in a grou p of healthy adults analyzed simultaneously. Forty-three infants aged 1-3 days and 38 healthy adults were recruited to the study to establis h the median, 10th, and 90th percentiles of the proportions and absolu te numbers of relevant lymphocyte subsets. The samples obtained from t he healthy adults served as a flow cytometry process control in additi on to providing a group comparator. The peripheral blood of the newbor ns (vs. adults) contained elevated proportions of total T cells (83% v s. 77%) and T helper cells (63% vs. 46%), with decreased proportions o f T suppressor/cytotoxic cells (23% vs. 28%) and NK cells (4% vs. 10.5 %). The newborns had a higher proportion (P < 0.0001) of immature B ly mphocytes compared with those of adults (CD10+CD19+, 1.5% vs. 0% and C D20+CD5+, 13% vs. 6%), and the proportion of activated T cells was sig nificantly lower (P < 0.0001; CD3+CD25+, 7.0% vs. 15%;CD3+HLA-DR+, 2.0 % vs. 6% and CD8 and CD57, 0.0% vs. 8.0%). In contrast, the proportion s of neonatal CD8 cells expressing CD28 (90.2% vs. 67.7%) and CD38 (96 .6% vs. 70.9%) were significantly higher (P < 0.0001). The reference r anges for 1-3-day-old healthy newborns generated in this study provide s a valuable tool for the assessment of immune abnormalities in very y oung infants. (C) 1998 Wiley-Liss, Inc.