OBJECTIVE: To study the changes of red cell immune function and T-lymphocyte subsets in children with bronchiolitis and their possible roles in the pathogenesis of bronchiolitis. METHODS: Forty-five children with bronchiolitis and 30 healthy controls were enrolled. Red cell immune complex rosette (RBC-ICR) and red cell C3b receptor rosette (RBC-C3bRR) were detected. The percentages of CD3+, CD4+ and CD8+ cells were assayed by flow cytometry. RESULTS: RBC-C3bRR［(13.6±6.2)% vs (18.0±7.4)%］and the percentage of CD8+ cells［(21.6±4.4)% vs (25.6±5.2) %］ in the bronchiolitis group were lower than those in the control group (P<0.01). The percentage of CD3+ cells ［(59.9±6.7)% vs (52.1±8.3)%］ and CD4+ cells［(53.5±6.2)% vs (46.8±4.9)%］and RBC-ICR［(8.3±3.5)% vs (6.1±2.5)%］in the bronchiolitis group were higher than those in the control group (P<0.01). The percentage of CD4+ cells was positively correlated with RBC-ICR (r=0.63,P<0.05) and negatively correlated with RBC-C3bRR (r=-0.82,P<0.01). CONCLUSIONS: There are dysfunctions of red cell immune and T-lymphocyte subsets in children with brochiolitis, which may play a role in the pathogenesis of brochiolitis.