Testicular FasL is expressed by sperm cells

Abstract

The testis is the main source of Fas ligand (FasL) mRNA in rodents; it is generally believed that this molecule, expressed on bordering somatic Sertoli cells, bestows an immune-privileged status in the testis by eliminating infiltrating inflammatory Fas-bearing leukocytes. Our results demonstrate that the attribution of testicular expression of FasL to Sertoli cells is erroneous and that FasL transcription instead occurs in meiotic and postmeiotic germ cells, whereas the protein is only displayed on mature spermatozoa. These findings point to a significant role of the Fas system in the biology of mammalian reproduction.testis ͉ immunoprivilege ͉ fertility

Testicular defense systems: immune privilege and innate immunity

“…75 FasL is predominantly expressed in male germ cells, but not in SCs. 33 Whether FasL that is expressed in the germ cells induces lymphocyte apoptosis and contributes to immune privilege within the seminiferous tubules remains to be investigated. Programmed death receptor-1/programmed death ligand-1 (PD-1/PD-L1) is another T-cell tolerance system.…”

“…31,32 Fas ligand (FasL) is abundantly expressed in male germ cells. 33 FasL-induced apoptosis of Fas-bearing lymphocytes is an important mechanism for suppression of immune responses. 34 However, whether the FasL expressed in germ cells contributes to testicular immune privilege remains to be elucidated.…”

Expression of the Fas-ligand gene in ejaculated sperm from adolescents with and without varicocele

“…Moreover, FasL has also been detected on the sperm cell surface [44]. This is especially interesting because it has been previously suggested that (i) FasL may be a protective mechanism so sperm may counteract uterine macrophages and (ii) FasL may present a competitive advantage over other sperm, stimulating apoptosis in adjacent cells [29].…”

“…Apoptosis may be activated through extrinsic mechanisms involving the interaction of Fas and its ligand, FasL [15][16][17]43], a system which controls homeostasis in various tissues [44]. Fas is a type I transmembrane protein that belongs to the tumor necrosis factor receptor superfamily.…”

“…FasL is produced as a type II membrane protein and is a member of the tumor necrosis factor family of proteins [34,[45][46][47]. Upon binding to FasL, Fas induces apoptotic activation of intracellular caspases, effector proteins, which in turn activate the cascade of events leading to cell death [27,41,44].…”