Presence of IL-18 in testicular tissue of fertile and infertile men.

Recently, IL-18 was identified in human testes. Moreover, an inverse correlation was found between the levels of IL-18 and the number and motility of spermatozoa. We examined the presence of IL-18 protein in normal and impaired spermatogenesis. Testicular tissue specimens were taken from 25 nonobstructive azoospermic patients undergoing testicular sperm extraction and from autopsies of three healthy controls. The presence of IL-18 in human testicular cells was examined by immunohistochemical staining of paraffin-embedded sections, using a specific antibody for human IL-18. In testicular tissue of healthy controls as well as in study cases, presence of IL-18 was identified in somatic, mitotic, meiotic and post-meiotic cells in correlation with their presence. In all patients, Leydig cells were less intensively stained. Mitotic cells were immunostained in the control group and less intensively in hypospermatogenesis and maturation arrest subgroups. Primary spermatocytes were in general most efficiently stained. The expression of IL-18 mRNA (as examined by real-time PCR analysis) showed significantly lower expression in testicular tissues with impaired spermatogenesis when compared to normal tissues. We report the first study demonstrating the presence of IL-18 in human testicular tissue at the protein level. The presence of this cytokine in somatic as well as in different types of germ cells may suggest its involvement in the regulation of the spermatogenic process and steroidogenesis under physiological and pathological conditions.