Objective: To investigate the role of increased seminal leukocytes in enhancing reactive oxygen species

(ROS) production by human spermatozoa.

Design: A prospective study. Setting: Male infertility clinic. Patient(s): Forty-eight infertile men.

Intervention(s): Standard semen analysis. Assessment of sperm nuclear DNA damage by sperm chromatin structure assay. Incubation of spermatozoa from nonleukocytospermic samples with blood neutrophils.

Main Outcome Measure(s): Spontaneous and phorbol 12-myristate 13-acetate (PMA)-induced ROS pro- duction in pure-sperm suspensions (after removal of leukocytes) as measured by a chemiluminescence assay.

Result(s): Levels of spontaneous and PMA-induced ROS production in pure-sperm suspensions from the infertile men with a diagnosis of leukocytospermia (n =  16) were significantly higher compared with the case of infertile men without leukocytospermia (n =32) and with the case of a control group of healthy volunteers (n  =13). A similar pattern of increased ROS was observed when spermatozoa were incubated with blood neutrophils. Leukocytospermia was associated with a significant decrease in sperm motility and increase in DNA damage.

Conclusion(s): Increased seminal leukocytes may play a role in stimulating ROS production by human spermatozoa. Such stimulation may be mediated via direct cell– cell contact or by soluble products released by leukocytes. Poor sperm quality in leukocytospermic samples may be due to leukocyte-mediated oxidative stress.