- Objective: To characterize and localize interleukin (IL)-1α and IL-1β in human sperm cells. Design: Prospective and comparative study. Setting: Andrology clinic of a university hospital. Patient(s): Two groups of normogonadotropic men: 17 fertile men (donors with proved fertility) and 8 oligoteratoasthenospermic infertile men. Intervention(s): None. Main Outcome Measure(s): Evaluation of IL-1α and IL-1β levels and expression in sperm cells by immunohistochemical staining, immunoassay, and Western blot analysis. Result(s): Both types of IL-1–like molecules (IL-1α and IL-1β) were expressed in the tail, neck, and head of sperm cells of fertile men and patients with oligoteratoasthenospermia. Swim-up sperm cells from fertile men and patients with oligoteratoasthenospermia secreted similar levels of IL-1–like molecules. The levels of IL-1β–like molecules were higher than those of IL-1α–like molecules in both groups. The expressed IL-1–like molecules were characterized by the presence a 60-kd protein for both IL-1α–like and IL-1β–like molecules. In some samples of both fertile men and infertile men with oligoteratoasthenospermia, 17-kd, 33-kd, and 45-kd IL-1β–like molecules were detected. Impairment of sperm function, such as decreased sperm count and motility and/or impaired morphology, was not related to the capacity of sperm cells to produce IL-1–like molecules. Conclusion(s): IL-1 molecules originating in sperm cells may play a role in the physiologic functions of sperm cells (autocrine effect) and/or in cell–cell interactions within the testis (paracrine effect).