Testicular FasL is expressed by sperm cells

The testis is the main source of Fas ligand (FasL) mRNA in rodents; it is g enerally believed that this molecule, expressed on bordering somatic Sertol i cells, bestows an immune-privileged status in the testis by eliminating i nfiltrating inflammatory Fas-bearing leukocytes. Our results demonstrate th at the attribution of testicular expression of FasL to Sertoli cells is err oneous and that Fast transcription instead occurs in meiotic and postmeioti c 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.