RESUMO
BACKGROUND: Acute chylothorax in neonates is a rare disease but results in significant loss of lymphatic cells. OBJECTIVES: The purpose of the study was to determine whether acute chylothorax in neonates results in quantitative changes of lymphocyte subpopulations in peripheral blood and chyle. METHODS: 6 neonates who had acute chylothorax after thoracic surgery due to transposition of the great arteries were prospectively enrolled in the study. Peripheral blood mononuclear cells (PBMC) and chylous fluid mononuclear cells (CFMC) including CD45RA+ and CD45RO+ T cells and the expression of the lymphocyte homing marker CD62L were investigated by fluorescence-activated cell sorting. RESULTS: In chyle, CD3+CD45RA+ T cells were significantly increased compared to peripheral blood (PMBC: median 65.8% of CD3+; range 32.3-76.9% vs. CFMC: 90.3%; 68.6-94.4%) (p = 0.02). In chyle, changes of percentages of the CD45RA+ were limited to CD8-expressing T cells (CD8+CD45RA+: PBMC: 77.3%; 69.3-85.6% vs. CFMC: 93.2%; 86.3-98.5%) (p = 0.02). The CD8+CD45RA+ were mainly CD62L+ (PBMC: 59.4%; 31.6-62.0% vs. CFMC: 87.8%; 62.7-90.7%) (p = 0.02). CONCLUSIONS: The study gives evidence that acute chylothorax in neonates results in immunophenotypic alterations and accumulation of certain T-cell subpopulations in the pleural cavity. Although limited by small numbers of patients due to the rare manifestation of the disease, we were able to demonstrate an abundance of CD8+CD45RA+ T cells expressing CD62L in the chyle compared to peripheral blood. However, whether CD62L expression may contribute to the accumulation of CD8+CD45RA+ T cells in chyle and whether quantitative changes of these specific cells are of clinical relevance has to be determined.