T-CELL AND MACROPHAGE SUBSETS IN THE BRONCHIAL WALL OF CLINICALLY HEALTHY-SUBJECTS

This study was conducted to obtain quantitative data on the numbers of T-cells and macrophage subsets in the normal bronchial wall of man, a nd, thus, produce a baseline against which the numbers of these cells present in inflamed bronchi may be judged. Bronchial biopsies were obt ained from 27 clinically healthy subjects attending hospital for elect ive orthopaedic operations. Eight of the subjects were smokers (median 3.5 pack-years), and eight were atopic as defined by skin prick test. Three to eight weeks after biopsy, subjects attended the lung functio n laboratory for spirometric testing and determination of provocative concentration of histamine producing a 20% fall in forced expiratory v olume in one second (PC20FEV1). The bronchial biopsies were frozen and cryostat sections prepared. These sections were investigated with imm unohistological techniques to reveal the presence and distribution of T-cell and macrophage subsets. Twenty six out of 27 subjects had spiro metric values within the normal range, but a wide spectrum of bronchia l reactivity was observed (PC20FEV, range 2-36 mg histamine). Using mo noclonal antibodies in immunohistological techniques, only small numbe rs of T-cells were seen, the majority being CD8+ cells in the epitheli um. In the underlying tissue, CD4+ cells, predominated (CD4/CD8 ratio, epithelium 1:9; underlying tissue 4:1). In both cases, approx. 50% of T-cells expressed the CD45Ro isotype. Small numbers of macrophages we re observed in all samples. The majority of these cells expressed a '' suppressor cell'' phenotype (RFD1+RFD7+), whilst only a small proporti on (median 11%) exhibited the phenotype of antigen presenting cells (R FD1+RFD7-). Only very low levels of human leucocyte antigen-DR (HLA-DR ) were recorded, both on the epithelium and underlying tissues. Smokin g status and atopy did not influence the numbers and distribution of t he T-cells and macrophages. These data offer, for the first time, a ba seline against which the severity of immunopathological reactions in t he bronchial wall may be evaluated.