Prospective study of leukocytes and leukocyte subpopulations in semen suggests they are not a cause of male infertility.

Objective: To determine the effects of leukocytes in semen on sperm quality and the ability to achieve conception.

Design: A prospective analysis of 512 couples attending a regional infertility clinic. Leukocyte subsets were quantified using a monoclonal antibody-based staining procedure. In addition to basic seminal parameters (density, motility, morphology, and antisperm antibodies), reactive oxygen species and immature germ cells were also quantified in the semen of each patient. The presence or absence of a treatment-independent conception was determined 22 months after the start of the study. Semen parameters were then related to the ability to conceive.

Setting: University-based center for reproductive medicine.

Participants: Success or failure to conceive was recorded from 512 couples. Couples were then selected to minimize the influence of any pathology of the female on outcome. A final study group of 229 couples, in which the women had regular menstrual cycles, ovulatory midluteal serum P levels of > 18 nmol/L, and patent fallopian tubes was finally selected for analysis.

Main Outcome Measure: Pregnancy.

Results: Leukocyte concentration (total or individual subsets) was not associated with either reduced semen quality or conception rates. Similarly, neither reactive oxygen species or antisperm antibody (immunobead) concentration had any bearing on the outcome. Of all semen parameters measured, only the level of immature germ cells was found to be negatively associated with the rate of conception.

Conclusion: Measurement of seminal leukocytes in routine semen analysis appears to be of little prognostic value with regard to male fertilizing potential. As reactive oxygen species and antisperm measurement were of similar predictive value, the term "immunologic male infertility" should be redefined.