Differential leucocyte detection by flow cytometry improves the diagnosis of genital tract inflammation and identifies macrophages as proinflammatory cytokine-producing cells in human semen.

Genital tract inflammation is considered as a major cause of male infertility with leucocytospermia as widely used diagnostic marker. However, threshold of 10(6) leucocytes ml(-1) recommended by the WHO is a matter of debate. Moreover, leucocyte subpopulations and their impact cannot be identified by the routine peroxidase method (POM). Ejaculates of subfertile men (n = 47) were analysed by flow cytometry (FACS) using a bead-based method. Leucocytes were identified by CD18 and further divided into macrophages (HLA-Dr+/CD66abce-) and neutrophils (HLA-Dr-/CD66abce+). IL-1β, TNF-α and IL-6 production was investigated in these subpopulations. It was found that CD18-positive cells correlated significantly with POM. However, only in samples with POM below 10(6) per millilitre, FACS detected significantly higher leucocyte numbers. Moreover, in 31% of these samples, FACS leucocyte detection reached threshold values greater than 1 × 10(6)  ml(-1) , fulfilling the criteria for diagnosis of leucocytospermia. Neutrophils were the predominating leucocyte population. Nevertheless, in 24% of samples, macrophages encountered more than 50% of leucocytes. Most interestingly, only macrophages produced significant amounts of IL-1β, TNF-α and IL-6. It is concluded that FACS improves detection and functional differentiation of seminal leucocytes as one of the diagnostic hallmarks of male genital tract inflammation.