title: Surfactant protein D regulates murine testicular immune milieu and sperm functions.
abstract: OBJECTIVE
  Surfactant protein D (SP-D), a pattern recognition protein that regulates inflammation and immune homoeostasis, is expressed by testicular germ cells under the influence of testosterone. This study investigates the role of SP-D in testicular immune privilege and sperm functions.
  
  
  METHODS
  Testicular levels of cytokines and immunoregulatory molecules were evaluated in lipopolysaccharide (LPS)-challenged SP-D gene knockout mice (SP-D-/-). Further, sperm functions were assessed by computer-assisted sperm analyser (CASA) and in vitro capacitation. The effect of a recombinant fragment of human SP-D (rhSP-D) on LPS-induced testicular inflammation and sperm motility was assessed in wild-type (WT) mice.
  
  
  RESULTS
  Endogenous absence of SP-D led to significantly increased testicular levels of immunosuppressive molecules, viz. serpina3, TGF-β1 and IL-10, and reduced levels of immune cell activation markers, CD86, IL-2 and ITGAX. These compensatory mechanisms resulted in markedly blunted levels of TNF-α, IL-12p40, MIP-1α, G-CSF and IL-6 in response to LPS challenge. Notably, exogenous supplementation of rhSP-D salvaged the WT mice from LPS-induced pro-inflammatory immune response and impairment of sperm motility by upregulating the levels of TGF-β1 and IL-10.
  
  
  CONCLUSIONS
  The study highlights the involvement of SP-D in maintenance of testicular immune privilege and its indirect contribution to male fertility.
authors.affiliation: Department of Innate Immunity, National Institute for Research in Reproductive Health (NIRRH), Indian Council of Medical Research (ICMR), Parel, Mumbai, India.
authors.forename: Sushama
authors.initials: S
authors.lastname: Rokade
authors.affiliation: Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge, UK.
authors.forename: Uday
authors.initials: U
authors.lastname: Kishore
authors.affiliation: Department of Innate Immunity, National Institute for Research in Reproductive Health (NIRRH), Indian Council of Medical Research (ICMR), Parel, Mumbai, India.
authors.forename: Taruna
authors.initials: T
authors.lastname: Madan
mesh_terms: D000818:Animals; D060833:Cellular Microenvironment; D005260:Female; D006801:Humans; D000073860:Immune Privilege; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D037663:Pulmonary Surfactant-Associated Protein D / Q000235:genetics / Q000378:metabolism*; D051192:Receptors, Pattern Recognition / Q000235:genetics / Q000378:metabolism*; D013094:Spermatozoa / Q000502:physiology*; D013737:Testis / Q000276:immunology*
chemical_list: D037663:Pulmonary Surfactant-Associated Protein D; D051192:Receptors, Pattern Recognition
keywords: capacitation; fertility; lipopolysaccharide; sperm motility; surfactant protein D; testis