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 Ϯ 2.55) and 10 (20 Ϯ 11.8) of dexamethasone therapy compared with before (30.36 Ϯ 6.41) or after treatment. The percentage of T cells was significantly lower on days 3 and 10 of dexamethasone therapy (mean Ϯ SEM; 58.09 Ϯ 1.93 and 60.09 Ϯ 2.47, respectively) compared with before (67.09 Ϯ 4.24) or after treatment. The absolute number of T cells was significantly lower on day 10 of therapy. The percentage of CD4 ϩ cells was significantly lower on days 3 (38.91 Ϯ 2.49) and 10 (40.45 Ϯ 2.24) of therapy, and this decrease persisted after dexamethasone was stopped (36.73 Ϯ 3.41). The absolute number of CD4 cells was significantly lower on day 10 (1328 Ϯ 216) of therapy and reached a nadir on day 56 (1143 Ϯ 106). Similarly, the CD4/CD8 ratio was also significantly lower on days 3 and 10 of treatment (1.56 Ϯ 0.18 and 1.64 Ϯ 0.14, respectively) and reached a nadir on day 56 (1.04 Ϯ 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.Bronchopulmonary dysplasia (BPD) is a chronic lung disease associated with mechanical ventilation in premature infants and a common cause of morbidity in the neonatal intensive care unit. The incidence of BPD is Յ40% among infants with respiratory distress syndrome who require mechanical ventilation. 1 Treatment with intravenous dexamethasone has been shown to shorten the duration of mechanical ventilation in premature infants, 2 and to improve pulmonary function. 3 However, dexamethasone therapy has many potential side effects in premature infants, including hyperglycemia, 4 hypertension, 5 cardiomyopathy, 6 adrenal suppression, 7-9 and gastrointestinal bleeding. 10 Dexamethasone has been shown to cause neutrophilia and eosinopenia 11,12 in addition to inhibition of colony formation of the hematopoietic progenito...

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