Reduced bronchial CD4⁺ T cell density in smokers with occupational asthma

T. Sjåheim ^1*, J. Kongerud ², . Bjørtuft ², P.A. Drabløs ³, D. Malterud ⁴, T.S. Halstensen ⁵

¹ Laboratory for mucosal immunology (LMI), Dept of Oral Biology, University of Oslo, Norway; and Dept of Respiratory Medicine, Rikshospitalet, Oslo, Norway
² Dept of Respiratory Medicine, Rikshospitalet, Oslo, Norway
³ Health Dept, Hydro Aluminium, Karmøy, Norway
⁴ Health Dept, Elkem Aluminium, Lista
⁵ Laboratory for mucosal immunology (LMI), Dept of Oral Biology, University of Oslo, Norway

^* To whom correspondence should be addressed. E-mail: tonebs{at}odont.uio.no.

	Abstract

Cigarette smoking may alter bronchial inflammation in asthma. Multicolour immunohistofluorescent examination on bronchial cryo sections was used to examine bronchial inflammatory cell infiltrate in patients with occupational asthma. Monoclonal antibodies to CD3, CD4, CD8, TCR-1, CD68 and HLA-DR were combined to identify T cell subsets and macrophages in bronchial biopsies from 20 workers with occupational asthma (12 smokers and 8 non-smokers), 15 healthy workers (7 smokers and 8 non-smokers) and 10 non-smoking, non-exposed controls.

The increased subepithelial CD4⁺ T cell density in non-smoking asthmatics was not present in smoking asthmatics, which had the lowest CD4⁺ T cells density of all groups. The decreased subepithelial CD4⁺ and CD8⁺ T cell density correlated with reduction in lung function (FEV₁ %), in smoking asthmatics, only. Although smoking asthmatics had significantly increased number of intraepithelial CD8⁺ T cells and macrophages compared to non-smoking asthmatics, the proportion of -T cells was significantly decreased in both asthmatic groups.

Smoking asthmatics had a distinct different distribution of T cell subsets compared to non-smoking asthmatics. The accumulation of subepithelial CD4⁺ T cells in non-smoking asthmatics appeared to be inhibited in smoking asthmatics, suggesting a smoking induced bronchial immune modulation, at least in occupational asthma in the aluminium industry.