Lymphocyte subpopulations in full-term septic neonates

Purpose: To estimate the absolute leukocyte and lymphocyte counts and relative and absolute sizes of CD19+ B lymphocytes, CD3+, CD4+, CD8+ and CD3+/HLA-DR+ T lymphocytes in full-term septic neonates and the influence of some perinatal risk factors on these lymphocyte subsets. Methods: Twenty-one septic and mechanically ventilated full-term neonates (13 boys and eight girls) and 15 healthy full-term neonates born vaginally with an Apgar score >9 and without hyperbilirubinemia were investigated. Two-color flow cytometric immunophenotyping with appropriate antibody panels using lysed whole vein blood was performed. Results: The mean relative and absolute sizes of CD19+ B lymphocytes, CD3+/CD8+ and CD3+/HLA-DR+ T lymphocytes in septic neonates did not differ significantly from control. In contrast, the mean relative sizes of CD3+ and CD3+/CD4+ T lymphocytes and the CD4+/CD8+ ratio in septic neonates were significantly higher than in healthy neonates. With regard to the absolute size in septic neonates, only CD4+ T cells were significantly higher compared with the control group. Perinatal risk factors (birth asphyxia, gestation and delivery complications) had no significant effect on the relative and absolute counts of all estimated lymphocyte subpopulations in septic neonates. Conclusions: Increases in the relative sizes of CD3+ and CD3+/CD4+ T lymphocytes and the CD4+/CD8+ ratio in full-term septic neonates provides important information about changes in cell-mediated immunity during the early neonatal period.