Characterization of tumour necrosis factor‐α‐related apoptosis‐inducing ligand and its receptors in the adult human testis

Tumour necrosis factor‐α‐related apoptosis‐inducing ligand (TRAIL) is a member of the tumour necrosis factor‐α (TNF‐α) family of cytokines which is known to induce apoptosis upon binding to its death domain‐containing receptors, DR4/TRAIL‐R1 and DR5/TRAIL‐R2. Two additional TRAIL receptors, DcR1/TRAIL‐R3 and DcR2/TRAIL‐R4, lack functional death domains and act as decoy receptors for TRAIL. In this study, the presence of TRAIL and its receptors was investigated by immunohistochemistry in adult human testes. In addition, TRAIL and its receptors were studied in terms of protein and mRNA using western blot analysis and RT–PCR respectively. TRAIL and its receptors were immunodetected according to the different testicular cell types: TRAIL, DR5/TRAIL‐R2 and DcR2/TRAIL‐R4 were localized in Leydig cells, DR4/TRAIL‐R1 was seen in peritubular and Sertoli cells whereas ligand and all receptors were detected in germ cells. Proteins and mRNA corresponding to TRAIL and its receptors were also identified in adult human testes. In conclusion, TRAIL and its receptors DR4/TRAIL‐R1, DR5/TRAIL‐R2, DcR1/TRAIL‐R3 and DcR2/TRAIL‐R4 are expressed in the human testis, and are predominantly localized in different germ cell types.