Peripheral blood T-cell subpopulations in the very low birth weight (less than 1,500-g) infant.

The development of monoclonal antibodies to cell-surface antigens has provided method for characterizing distinct subpopulations of T-cells. In the present study we have quantified peripheral blood T-cell subpopulations in premature infants born weighing less than 1,500 g (1123 +/- 223 g) and ranging in gestational age from 25 to 32 weeks. The relative proportion of T4 cells in the very low birth weight (VLBW) infants was markedly higher at 1 week and 1 month of age (mean +/- SEM; 67.5 +/- 4.1 and 59.2 +/- 1.6) than in adult controls (47.2 +/- 1.5). The percentage of T4 cells remained elevated until 6 months of age, when it decreased to a level comparable to that in adults. In contrast, the proportion of T8 cells was significantly lower than the adult level at 1 week and 1 month of age. The T4/T8 ratio in the VLBW infants was higher at 1 week (4.3 +/- 0.5) and 1 month (3.5 +/- 0.2) than in adult controls (2.0 +/- 0.1). Thereafter, the T4/T8 ratio decreased but was still significantly higher than that in adult controls at 6 months of age (2.6 +/- 0.2). The absolute numbers of total T-cells (T3) and T8 and T4 cells were significantly higher in VLBW infants. The numbers of T8 cells were significantly lower in the first month of life than at 3-6 months of age. These alterations in the T-cell subsets in the first 6 months of life suggest that postnatal T-cell phenotypic changes in VLBW infants may parallel the T-cell ontogenetic process which occurs during the last trimester of pregnancy in full-term infants.