256 Activation of Circulating CD4+ T-Cells in Preterm Infants with RDS

Abstract

Background: In preterm infants with respiratory distress syndrome (RDS), early activation of circulating phagocytes is present as a sign of systemic inflammation. Phagocytes interact closely with lymphocytes. The role of lymphocytes in the pathogenesis in RDS is unclear. The aim of this study was to evaluate lymphocyte subsets and their activation during the first postnatal week in preterm infants with and without RDS.Methods: Peripheral blood samples from 58 preterm infants [gestational age (GA) 27.3(26.3–29.4) wks; birth weight (BW) 930(733–1200)g] were taken on postnatal days 1, 3 and 7 (d1, d3, and d7). T-lymphocyte subpopulations (CD4+, CD8+ and NK-cells) and proportions of T-cells expressing activation marker CD54 (ICAM-1) were analyzed by flow cytometry using fluorescent antibodies. Infants who had increased C-reactive protein levels (<20mg/L) were excluded from the analysis (N=10) to control activation of lymphocytes due to infection. The remaining infants were assigned to two groups according to whether they had RDS or not. The results are given as absolute cell counts (10E9/L) and proportions of CD54+CD4+ cells of CD4+T-lymphocytes (%), in medians (quartiles).Results: 25 infants had RDS [GA 26.7(25.3–27.6)wks, BW 860(700–1060)g], and 23 infants had not [GA 32.7(30.6–33.9)wks, BW 1500(1380–1990)g]. Infants with RDS had significantly lower GA and BW than those without RDS, both p<0.001. Infants with RDS had significantly lower blood T-lymphocyte count on d3 than did infants without RDS (p=0.028). Compared with infants without RDS, infants with RDS had lower CD4+T-cell counts on d3 (p=0.034) and CD8+T-cell counts on d1 (p=0.036) and on d3, although not statistically significant (p=0.067). In infants with RDS on d1, d3, and d7, a greater proportion CD4+ T-cells was CD54-positive than in infants without RDS [d1: 4.3(1.4–10.0) vs. 2.1(0.8–2.8), p=0.001; d3: 4.0(1.4–13.0) vs 1.8(0.8–3.0)%, p=0.009; d7: 5.4(2.6–9.9) vs 2.5(1.7–3.9), p=0.014]. There was no correlation between gestational age and proportions of CD4+CD54+-cells.Conclusion: In preterm infants with RDS, the absolute numbers of circulating T-cells are low and the peripheral blood CD4+ T-lymphocytes have more active immuophenotype than in infants without RDS. These results indicate an activation of circulating lymphocytes in RDS. The significance of T-cell activation in the inflammatory process related to RDS and development of chronic complications, such as bronchopulmonary dysplasia, remains to be elucidated.