Sex dependent differences 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 frequ ently but a possible relation to sex has not, to our knowledge, previously been examined. The effect of age and sex on the composition of lymphocyte s ubsets in bronchoalveolar lavage (BAL) fluid and peripheral blood was there fore examined. Methods-Bronchoscopy with lavage was performed in 32 healthy non-atopic, no nsmoking volunteers (16 women aged 26-63 years (mean 44) and 16 men aged 23 -63 years (mean 39)). Cytospin preparations for differential counts of BAL fluid cells and surface antigen expression of lymphocytes from BAL fluid an d blood were analysed by flow cytometry. Results-Most parameters in the BAL fluid changed with age in women. The per centage of CD4+ lymphocytes increased with age from a mean of 48 (SD10)% in women aged less than or equal to 40 years to 69 (11)% in women aged > 43 y ears (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 w ith 2.1 (0.7) in those aged less than or equal to 40 years (p <0.0001). Wom en aged >43 years differed from men aged >43 years as well as from younger subjects of both sexes with respect to CD4+ cells and CD4/CD8 ratio, and fr om younger women with respect to CD8+ cells. There was no age related chang e in the CD4/CD8 ratio in blood. No sex related differences were seen in th e blood or BAL fluid of adults below the age of 40 years. Conclusions-The composition of lymphocytes with different 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 w hich are observed predominantly in women.