ABSTRACT
<p><b>OBJECTIVE</b>To investigate the changes and clinical significance of lymphocyte subsets in infants with bronchitis, bronchopneumonia, and bronchiolitis.</p><p><b>METHODS</b>A total of 111 children with bronchitis, 418 children with bronchopneumonia, and 83 children with bronchiolitis were enrolled as disease groups, and 235 healthy children were enrolled as control group. Flow cytometry was applied to measure lymphocyte subsets.</p><p><b>RESULTS</b>The bronchitis group had significantly lower numbers of T cells and CD3+CD8+ T cells than the control group (P<0.05). The bronchopneumonia group had significantly lower numbers of T cells and CD3+CD8+ T cells, a significantly higher number of T helper (Th) cells, and a significantly higher CD4/CD8 ratio than the control group, as well as a significantly higher number of Th cells than the bronchitis group. Compared with the children with mild bronchopneumonia, those with severe bronchopneumonia showed a reduction in T cells and an increase in B cells (P<0.05). The bronchiolitis group had a significantly higher number of Th cells, a significantly higher CD4/CD8 ratio, and a significantly lower number of CD3+CD8+ T cells than the control group (P<0.01). The disease groups showed a significantly higher number of B cells and a significantly lower number of natural killer cells than the control group (P<0.05).</p><p><b>CONCLUSIONS</b>A low, disturbed cellular immune function and a high humoral immune function are involved in the development and progression of lower respiratory tract infectious diseases. The changes in immune function are related to the type and severity of diseases.</p>