OBJECTIVETo investigate the characteristics of immune function in newborn infants of different gestational ages.

METHODSA total of 115 premature infants free of infection between June 1, 2012 and June 1, 2013 were divided into two groups according to their gestational age at birth: early preterm infant group (28-33+6 weeks, n=57) and late preterm infant group (34-36+6 weeks, n=58). Meanwhile, 88 full-term infants (37-41+6 week) were recruited to the control group. Venous blood samples were collected within 24 hours after birth. The percentages of lymphocyte subsets, such as CD3+, CD4+, CD8+, and CD19+ T cells and natural killer (NK) cells were measured by flow cytometry, and the absolute count of each population was calculated using the results from routine blood work. Concentrations of serum IgG, IgA, and IgM were measured by immunoturbidimetry.

RESULTSBoth preterm infant groups had significantly higher percentages of CD3+ and CD4+ T cells and CD4+/CD8+ ratio (P<0.05) and significantly lower percentages of CD8+ and CD19+ T cells and NK cells (P<0.05), as compared with the full-term infant group. The absolute counts of total lymphocytes, CD3+, CD4+, CD8+, and CD19+ T cells, and NK cells in both preterm infant groups were significantly lower than those in the full-term infant group (P<0.05), and the above parameters in the late preterm infant group were significantly higher than those in the early preterm infant group (P<0.05). Both preterm infant groups showed significantly lower concentrations of serum IgG than the full-term infant group (P<0.05), while no significant differences in concentrations of serum IgA and IgM were observed between the three groups (P>0.05).

CONCLUSIONSNeonatal gestational age has an effect on cellular and humoral immunity. The immune function gradually improves with increasing gestational age.