Analysis of sperm movement in relation to the oxidative stress created by leukocytes in washed sperm preparations and seminal plasma

The addition of luminol to unprocessed semen samples resulted in the generation of chemiluminescent signals, the intensity of which was highly correlated with the level of leukocyte contamination. Despite the spontaneous oxidant-generating capacity of seminal leukocytes, no correlations were observed between leukocyte contamination and the fertility status of the subjects or any aspect of the semen profile, including the motility of the spermatozoa or their performance in a hyaluronate penetration assay. Luminol-dependent chemiluminescence and leukocyte contamination were also correlated in washed sperm suspensions prepared either by repeated centrifugation or on discontinuous Percoll gradients. However, in such sperm suspensions, the spontaneous generation of oxidants by contaminating leukocytes (> 2 x 10(4) leukocytes/ml) was invariably associated with a decreased capacity for movement. Moreover, causative associations between leukocyte contamination, reactive oxygen species generation, lipid peroxidation and impaired sperm motility were revealed by experiments involving the selective addition or removal of activated leukocytes. From these observations we can conclude that low concentrations of leukocytes are a common feature of the human ejaculate and can impair sperm function, particularly in the absence of seminal plasma. These findings have implications for our understanding of the importance of leukocytospermia in defining the fertility of human spermatozoa in vivo and in vitro.