A comparison of the expression of lymphocyte activation markers in blood, bronchial biopsies and bronchoalveolar lavage: evidence for an enrichment of activated T lymphocytes in the bronchoalveolar space

In this study healthy never-smoking subjects (n = 18) were recruited from a population study. Bronchoalveolar lavage (BAL), blood lymphocytes and bron chial biopsies, analysed both in the epithelium and lamina propria, were st ained for T and B lymphocytes, natural killer (NR) cells and different subp opulations of T lymphocytes. In BAL, significantly higher proportions of T lymphocytes (CD3), T lymphocyte activation markers; HLA-DR, CD26(+), CD49a( +), CD54(+) and CD69(+), helper T (CD3(+)4(+)) and memory helper T lymphocy tes (CD4(+)45RO(+)29(+)) and memory T lymphocytes (CD3(+)45RO(+)) were foun d, compared to blood. However, the proportion of IL-2 receptor-positive T l ymphocytes (CD25(+)) was lower in BAL than in blood. A previously described higher ratio of CD3(+)4(+)/CD3(+)8(+) in BAL than in blood (3.4 vs 1.7; P = 0.001) was confirmed. In bronchial biopsies, we found significantly highe r numbers of CD8(+) cell profiles per mm(2) in the epithelial compared to t he lamina propria compartment. We conclude that healthy never-smoking men have higher levels of activated memory T lymphocytes in BAL than in blood, and that the T-cell subpopulatio ns differ in the epithelial compared to the lamina propria compartment in t he bronchial mucosa and these compartments should be analysed separately. I t is reasonable to think that there is a gradient from blood to the airway lumen where T cells are recruited from blood to take part in the defense to wards damaging agents. (C) 1999 Harcourt Publishers Ltd.