Seminal plasma pro-inflammatory cytokines interferon-γ (IFNG) and C-X-C motif chemokine ligand 8 (CXCL8) fluctuate over time within men.

STUDY QUESTION

Do seminal plasma pro-inflammatory cytokines interferon-γ (IFNG) and C-X-C motif chemokine ligand 8 (CXCL8) vary within individual men over time?

SUMMARY ANSWER

IFNG exhibits substantial variation that is independent of duration of abstinence but correlates with lipopolysaccharide (LPS) content, while CXCL8 varies moderately in association with duration of abstinence.

WHAT IS KNOWN ALREADY

Pro-inflammatory cytokines IFNG and CXCL8 in seminal fluid can adversely impact male and female fertility. Other cytokines as well as sperm parameters fluctuate considerably within individuals over time, but whether IFNG and CXCL8 vary similarly, and the determinants of variance, are unknown.

STUDY DESIGN, SIZE, DURATION: Between two and seven semen samples were collected from 14 proven fertile donors at 6-10 week intervals over the course of ~12 months, to assess variation over time in cytokines and LPS, and to investigate relationships with sperm parameters and possible regulatory factors.

PARTICIPANTS/MATERIALS, SETTING, METHODS: The concentrations and total amounts per ejaculate of IFNG and CXCL8 were determined using commercial ELISA. Sperm parameters were assessed according to World Health Organization (WHO) IV standards and LPS was measured by limulus amebocyte lysate (LAL) assay. Mixed model analysis was utilized to determine the relative contribution of between- and within-individual factors in explaining variance. Relationships between cytokines, LPS and sperm parameters, as well as effect of age and duration of abstinence, were investigated by correlation analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Within-individual variability contributed to total variance particularly for both IFNG, CXCL8 and LPS, and was a stronger determinant than between-individual variability for IFNG and LPS. Normal sperm motility correlated inversely with CXCL8, and sperm concentration correlated inversely with LPS. Duration of abstinence was a determinant of total CXCL8, but not IFNG or LPS. Associations between LPS, IFNG and CXCL8 suggest IFNG and perhaps CXCL8 are influenced by microbial populations.

LIMITATIONS, REASONS FOR CAUTION: A limited number of donors from a single clinic were investigated. Clinical information on complete microbiology, BMI, nutrition, smoking and other lifestyle factors was unavailable. Further studies are required to determine whether the findings can be generalized to larger populations and different ethnicities.

WIDER IMPLICATIONS OF THE FINDINGS

These data reveal substantial variation over time in pro-inflammatory seminal fluid cytokines and imply existence of microbial or other environmental regulatory factors.

STUDY FUNDING/COMPETING INTEREST(S): This study was supported by grants from the National Health and Medical Research Council of Australia. The authors have no competing interests to disclose.