CXCL8 and gram-negative bacterial infections: Progesterone has been shown to significantly reduce IL-4-induced macrophage expression, IL-8, and Toll-like receptors 2 and 4 triggered by lipopolysaccharides in the cervix and placenta [35, 36]. In a clinical trial, 17α-hydroxyprogesterone caproate treatment was shown to reduce IL-1β but not IL-6, IL-8, and TNF in peripheral blood samples in vitro models of Gram-positive and Gram-negative bacterial infection [15].