Cicinelli et al. (2009) isolated E. coli in 11% of women with human CE in an infertility cohort. Indeed, the cell wall endotoxin produced by E coli, lipopolysaccharide (LPS) is known to induce the upregulation of plasma cells following infection with E. coli in humans (Kimura et al. 2019, Sola-Leyva et al. 2021). In the cow, LPS is known to induce endometrial inflammation by binding to TLR4 on the surface of endometrial cells and initiating a downstream cascade of inflammatory mediators (Jiang et al. 2021). Here, TLR4 is linked to cholesteryl ester measurement.