Evaluation of lymphocyte phenotype and phytohemagglutinin response in healthy very low birth weight infants

Sixteen healthy very low birth weight infants (VLBWI) were studied in a serial fashion over a 3-week period. Subjects were evaluated for lymphocyte phenotype, phytohemagglutinin (PHA) response, and metabolic status including weight, blood urea nitrogen, creatinine, albumin, pH, calcium, phosphorus, and ammonia. Lymphocyte phenotype determination showed a decreased proportion of CD3+ cells (66.8 ± 10.4 vs 75.9 ± 6.1, P < 0.02) in VLBWI. When subsets of the CD4+ population were examined, VLBWI had a lower proportion of CD4+ CD29+ cells (8.2 ± 5.8% vs 23.5 ± 8.0%, P < 0.0001) than adults and a higher proportion of CD4+ CD45R+ cells (35.6 ± 12.4% vs 22.2 ± 7.4%, P < 0.03). The CD4+ subsets in VLBWI were similar to those seen in term infants. The peak PHA response in VLBWI was greater than that of adults ( P < 0.01). There was little change in the immune measurements over the 3-week study period. There were no strong correlations between any of the immunological measurements and the metabolic measurements except that the proportion of CD8+ cells increased with birth weight. Our findings demonstrate that immune measurements in healthy VLBWI differ from values found in adults but are similar to those of full-term infants. Lower proportions of the CD4+ CD29+ cells (the helper/inducer subset for antibody production) may contribute to some of the differences in immune function reported in neonates.