Effect of dexamethasone on lymphocyte subpopulations in premature infants with bronchopulmonary dysplasia.

Objective: This study was designed to determine the effect of dexamethasone treatment on peripheral blood lymphocyte counts and subpopulations in premature infants with bronchopulmonary dysplasia (BPD).

Study Design: Peripheral blood lymphocyte subpopulations in 12 premature infants with BPD were analyzed before treatment with a 6-week course of dexamethasone (day 0), on days 3 and 10 of treatment, and 2 weeks after discontinuing dexamethasone therapy (day 56). Lymphocyte immunophenotypes were determined using direct two-color immunofluorescent staining followed by flow cytometry.

Results: The percentage of lymphocytes was significantly lower on days 3 (17.55 +/- 2.55) and 10 (20 +/- 11.8) of dexamethasone therapy compared with before (30.36 +/- 6.41) or after treatment. The percentage of T cells was significantly lower on days 3 and 10 of dexamethasone therapy (mean +/- SEM; 58.09 +/- 1.93 and 60.09 +/- 2.47, respectively) compared with before (67.09 +/- 4.24) or after treatment. The absolute number of T cells was significantly lower on day 10 of therapy. The percentage of CD4+ cells was significantly lower on days 3 (38.91 +/- 2.49) and 10 (40.45 +/- 2.24) of therapy, and this decrease persisted after dexamethasone was stopped (36.73 +/- 3.41). The absolute number of CD4 cells was significantly lower on day 10 (1328 +/- 216) of therapy and reached a nadir on day 56 (1143 +/- 106). Similarly, the CD4/CD8 ratio was also significantly lower on days 3 and 10 of treatment (1.56 +/- 0.18 and 1.64 +/- 0.14, respectively) and reached a nadir on day 56 (1.04 +/- 0.13).

Conclusion: Dexamethasone significantly reduced the percentage and absolute number of lymphocytes, T cells, and CD4 cells, as well as the CD4/CD8 ratio. A reduction in CD4 cells and in the CD4/CD8 ratio persisted 2 weeks after dexamethasone therapy was stopped. In contrast, the absolute number of B cells increased transiently, and CD8 cells were unaffected by dexamethasone. This alteration in lymphocyte subpopulations may help account for the clinically beneficial anti-inflammatory effect of dexamethasone in the treatment of BPD complicated by respiratory failure. The dexamethasone-induced decrease in CD4 cells may also increase the susceptibility of these infants to infection.