Background:
Neutrophils (polymorphonuclear leukocytes, PMNs) have long been underestimated in the context of autoimmunity. To elucidate their role from a sex-specific perspective, an immunoendocrinological framework offers a compelling investigative approach. We hypothesize that the sex hormone 17-β-estradiol (E2) and the endocrine-disrupting chemical bisphenol A (BPA) modulate PMN functions in a sex- and concentration-dependent manner. In addition, we consider the potential confounding effects of centrifugation protocols employed during PMN isolation.

Methods:
PMNs from healthy women and men were incubated with different concentrations of E2 (zero; low: 0.01 µM; high: 5µM) and BPA (zero; low: 1.6 µM; high: 16 µM). Migration behavior was assessed using live-cell imaging (n = 6 per concentration). Changes in cell surface expression and oxidative burst were quantified by flow cytometry (n = 12 per concentration).

Results:
Among samples from females, low doses E2 and BPA significantly reduced chemotactic migration. High substance concentrations led to a significant track length increase. Samples from males showed impaired migration after BPA incubation and increased migration behavior in the presence of E2 in both concentrations. Partially altered antigen expression was seen only in samples from females. Hereby, both concentrations of the tested substances caused reduced CD11b expression. Low dose E2 increased CD66b expression, low dose BPA induced higher LOX-1 expression. At the low concentration level, both substances led to an increase in Phorbol 12-myristate 13 acetate-stimulated oxidative burst. For PMNs from women, this also applied to high dose E2.

Conclusion:
Different concentrations of the hormone E2 and the endocrine-disrupting chemical BPA modulated neutrophil functions and phenotypes. The effects appeared to be sex-specific, providing a possible explanation for sex-specific immune responses. The data are consistent with the hypothesis that centrifugation impairs PMN functions and showed remaining substance effect despite of centrifugation.