Expression of oestrogen and progesterone receptors by mast cells alone, but not lymphocytes, macrophages or other immune cells in human upper airways

Background-Nasal polyposis often coexists with asthma in airway inflammator y conditions characterised by the infiltration of a range of immune cells. A potentially important role for ovarian hormones has been implicated in ai rway inflammation but the cellular target for such action is not known. Methods-Expression of oestrogen receptors (ER) and progesterone receptors ( PR) was examined using immunohistochemistry in formalin fixed nasal polyp t issues from 47 subjects. The cells positive for ER or PR were confirmed by spatial location, dual immunolabelling, and histochemical staining. Results-Consistent with the known features of nasal polyps, CD4+ (T helper/ inducer), CD8+ (cytotoxic/supressor), CD68+ (macrophages), mast cells, eosi nophils and neutrophils were all clearly detected by their relevant monoclo nal antibodies or appropriate histochemical staining, but only mast cells t ested positive for ER/PR labelling with their polyclonal and monoclonal ant ibodies. The frequencies for expression were 61.7% for ER positive and 59.6 % for PR positive cells. The expression of ER/PR was independent of patient sex and age but was highly correlated with the numbers of mast cells (r = 0.973, p<0.001 for ER; r = 0.955, p<0.001 for PR). Fewer than 5% of mast ce lls were found to be negative for ER/PR expression. Conclusions-Mast cells alone, but not lymphocytes, macrophages, or other im mune cells, express ER/PR in human upper airways. Numerous ER/PR positive m ast cells exist in nasal polyps, indicating that this may be a major route for the involvement of sex hormones in airway inflammation when exposed to the higher and varying concentration of oestrogen and progesterone characte ristic of females.