Sex dependent diVerences in physiological ageing in the immune system of lower airways in healthy non-smoking volunteers: study of lymphocyte subsets in bronchoalveolar lavage fluid and blood

Background—Age related changes in the immune system have been studied frequently but a possible relation to sex has not, to our knowledge, previously been examined. The eVect of age and sex on the composition of lymphocyte subsets in bronchoalveolar lavage (BAL) fluid and peripheral blood was therefore examined. Methods—Bronchoscopy with lavage was performed in 32 healthy non-atopic, nonsmoking volunteers (16 women aged 26–63 years (mean 44) and 16 men aged 23–63 years (mean 39)). Cytospin preparations for diVerential counts of BAL fluid cells and surface antigen expression of lymphocytes from BAL fluid and blood were analysed by flow cytometry. Results—Most parameters in the BAL fluid changed with age in women. The percentage of CD4+ lymphocytes increased with age from a mean of 48 (SD10)% in women aged <40 years to 69 (11)% in women aged >43 years (p=0.001). The percentage of CD8+ lymphocytes tended to decrease with age and the CD4/ CD8 ratio was 5.8 (1.2) in women aged >43 years compared with 2.1 (0.7) in those aged <40 years (p<0.0001). Women aged >43 years diVered from men aged >43 years as well as from younger subjects of both sexes with respect to CD4+ cells and CD4/CD8 ratio, and from younger women with respect to CD8+ cells. There was no age related change in the CD4/CD8 ratio in blood. No sex related diVerences were seen in the blood or BAL fluid of adults below the age of 40 years. Conclusions—The composition of lymphocytes with diVerent phenotypes in the lower respiratory tract changes with age in women but not in men. This may have implications for some clinical conditions such as chronic dry cough which are observed predominantly in women. (Thorax 2001;56:450–455)