- Problem This study examined the effect of intraperitoneal administration of lipopolysaccharide (LPS) to adult male mouse on the expression levels of interleukin-18 (IL-18), IL-18 receptor (IL-18R) and the IL-1β converting enzyme (ICE) (IL-18 family) in their testes and spleen (control). Method of study Adult mice were injected (intraperitoneally; i.p.) with saline (control) or LPS (2, 20, 100 μg/mL; 100 μL/mouse). After 3 and 24 hr, testes and spleen were collected. Testicular tissue was examined for IL-18 (by ELISA, real time PCR, and western blot analysis), IL-18R and ICE (western blot and real time PCR analysis) and spleen tissue was examined for the IL-18 family by real time PCR analysis. Student’s t-test was used for statistical analysis. Results Homogenates of mouse testes contain and express basal levels of IL-18, ICE and IL-18 R. The expression levels of IL-18, ICE and IL-18R were significantly increased 3 and 24 hr after intraperitoneal injection of LPS to mature mouse, as examined by ELISA, western blot and real time PCR analysis. However, the expression levels of IL-18, ICE and IL-18Rα in the spleen increased significantly only after 24 hr of LPS stimulation, as examined by real time PCR. Conclusion Our results demonstrate that LPS increases the expression levels of the IL-18 family in mouse testis and spleen, but the time of expression differs between the two organs. The presence of IL-18 in the testes might be involved in the regulation of physiological and infection/inflammatory processes, and may be part of the autocrine/paracrine factors that control spermatogenesis. Further studies should be performed to confirm this possibility.