β-defensins and the epididymis： contrasting influences of prenatal, postnatal, and adult scenarios

β-defensins are components of host defense, with antimicrobial and pleiotropic immuno-modulatory properties. Research over the last 15 years has demonstrated abundant expression of a variety of β-defensins in the postnatal epididymis of different species. A gradient of region- and cell-specific expression of these proteins is observed in the epithelium of the postnatal epididymis. Their secretion into the luminal fluid and binding to spermatozoa as they travel along the epididymis has suggested their involvement in reproduction-specific tasks. Therefore, continuous attention has been given to various β-defensins for their role in sperm function and fertility. Although β-defensins are largely dependent on androgens, the underlying mechanisms regulating their expression and function in the epididymis are not well understood. Recent investigation has pointed out to a new and interesting scenario where β-defensins emerge with a different expression pattern in the Wolffian duct, the embryonic precursor of the epididymis, as opposed to the adult epididymis, thereby redefining the concept concerning the multifunctional roles of β-defensins in the developing epididymis. In this review, we summarize some current views of β-defensins in the epididymis highlighting our most recent data and speculations on their role in the developing epididymis during the prenatal-to-postnatal transition, bringing attention to the many unanswered questions in this research area that may contribute to a better understanding of epididymal biology and male fertility.

Interactions of complement proteins C1q and factor H with lipid A and Escherichia coli:further evidence that factor H regulates the classical complement pathway

Proteins of the complement system are known to interact with many charged substances.We recently characterized binding of C1q and factor H to immobilized and liposomal anionic phospholipids.Factor H inhibited C1q binding to anionic phospholipids,suggesting a role for factor H in regulating activation of the complement classical pathway by anionic phospholipids.To extend this finding,we examined interactions of C1q and factor H with lipid A,a well-characterized activator of the classical pathway.We report that C1q and factor H both bind to immobilized lipid A,lipid A liposomes and intact Escherichia coli TG1.Factor H competes with C1q for binding to these targets.Furthermore,increasing the factor H:C1q molar ratio in serum diminished C4b fixation,indicating that factor H diminishes classical pathway activation.The recombinant forms of the Cterminal,globular heads of C1q A,B and C chains bound to lipid A and E.coli in a manner qualitatively similar to native C1q,confirming that C1q interacts with these targets via its globular head region.These observations reinforce our proposal that factor H has an additional complement regulatory role of down-regulating classical pathway activation in response to certain targets.This is distinct from its role as an alternative pathway downregulator.We suggest that under physiological conditions,factor H may serve as a downregulator of bacterially-driven inflammatory responses,thereby finetuning and balancing the inflammatory response in infections with Gram-negative bacteria.