BACKGROUND Bronchiectasis is a chronic suppurative lung disease characterised by irreversible dilation of the bronchi and persistent purulent sputum. The immunopathology of the disease was studied using a quantitative immunostaining technique with particular reference to T lymphocytes, macrophages, and granulocytes.

RESULTS There was a mononuclear cell infiltrate in both patients with bronchiectasis and normal controls, but an overall increase in total leucocyte cell numbers (CD45+ cells) was identified in those with bronchiectasis (median values 422 cells/mm² versus 113 cells/mm² in control tissue, p<0.001). Intense infiltration of CD3+ T lymphocytes was observed compared with healthy controls (292 cells/mm² and 40 cells/mm², respectively, p<0.001). This comprised predominantly CD4+ T cells (118 cells/mm²) rather than CD8+ T cells (47 cells/mm²). CD3+ cell counts were reduced in those subjects on inhaled steroids compared with those not receiving inhaled steroids (197 cells/mm² versus 369 cells/mm², p<0.05), as were CD4+ cell counts (82 cells/mm² versus 190 cells/mm², p<0.05). Neutrophil and macrophage cell numbers were also increased in patients with bronchiectasis (114 cells/mm² and 213 cells/mm², respectively) compared with controls (41 neutrophils/mm² and 40 macrophages/mm²). EG2+ (activated) eosinophil numbers were much lower than T cells, macrophages, and neutrophils in patients with bronchiectasis but were increased compared with controls (36 cells/mm² versus 0 cells/mm², p<0.001). In view of the markedly increased neutrophil counts in patients with bronchiectasis, biopsy specimens were immunostained for interleukin 8 (IL-8) which was highly significantly increased compared with controls (47 cells/mm² versus 15 cells/mm², p<0.01). IL-8+ cells were less prominent in steroid treated patients than in patients not receiving treatment (30 cells/mm² versus 60 cells/mm², p<0.05). A further characteristic of bronchiectasis was mucous gland hypertrophy. Gland area comprised up to 40% of the tissue in some bronchiectasis sections while no hypertrophy was noted in control biopsy specimens (p<0.05).

CONCLUSION Airway inflammation in bronchiectasis is characterised by tissue neutrophilia, a mononuclear cell infiltrate composed mainly of CD4+ T cells and CD68+ macrophages, and increased IL-8 expression. Inhaled corticosteroid treatment in patients with bronchiectasis is associated with a less marked infiltration by T cells and IL-8+ cells within the bronchial mucosa, although this finding requires confirmation in a prospective placebo controlled trial.