Regulatory T cells vary over bleeding segments in asthmatic and non-asthmatic women.

Sex hormones may play an important role in observed gender differences in asthma incidence and severity. Regulatory T cells (Treg cells) are presumed to be involved in asthma and may vary with hormone levels. To investigate the effects of sex hormones on levels of Treg cells (percentage of CD4+CD25+Foxp3+ lymphocytes that are CD127-), a cohort of 13 women (6 with and 7 without an asthma diagnosis) had blood drawn multiple times over the course of a bleeding segment (bleeding interval plus the following bleeding-free interval) and collected urine samples daily for measurement of estrogen (estrone E1C) and progesterone (pregnanediol-glucuronide PDG) metabolites. The samples from non-asthmatic women indicated no association between bleeding segment day and Treg cells. Asthmatic women showed a 3% increase in Treg cell percentage with each successive day over the bleeding segment. Among non-asthmatic women, Treg cell percentages were not associated with PDG levels on the same day, or 1, 2 or 3 days before Treg cell measurement. E1C was positively correlated with the Treg cell percentage measured only on the same day - a 5% increase in E1C was associated with a 1.4% increase in Treg cell percentage. Among asthmatic women, only E1C was associated with Treg cell percentages after adjusting for PDG on the same day and 1 and 2 days before Treg cell measurement. A 5% increase in E1C was associated with a 2.3% increase in Treg cell percentage. A larger study of contiguous cycles to better determine within-woman cyclicity of the observed patterns is needed.