Lymphocytic inflammation in childhood bronchiolitis obliterans

Childhood bronchiolitis obliterans (CBO) is an infrequent, severe disorder characterized by persistent obstructive respiratory symptoms after an acute episode of bronchiolitis. The viral etiology is most common, and adenovirus is the most frequently identified causative agent. Pathologically, the disease is characterized as constrictive type BO, with variable degrees of chronic inflammation and fibrosis in the bronchioles. The nature of the cellular infiltrate is largely unknown, and its characterization may provide better understanding of the disease and offer clues for therapy. Therefore, the aim of the present study was to characterize the inflammatory infiltrate in the bronchioles of 23 open lung biopsies of children with CBO and to compare this to the infiltrate in histologically normal airways. Our results show that CD3+ T cells were the most frequent cell type observed in CBO, with a predominance of the CD8+ T-cell subtype. When compared to the control group, there was a larger number of CD8+, CD4+, CD20+, granzyme B+, and perforin+ lymphocytes in the CBO group. Further studies are needed to address the role of different cell types in the development of CBO.