Transforming growth factor-beta (TGF beta) in porcine seminal plasma

Bioactive factors in seminal plasma induce cellular and molecular changes in the female reproductive tract after coitus. An active constituent of seminal plasma in mice and humans is the potent immune-modulating cytokine transforming growth factor-beta (TGF beta). To investigate whether TGF beta is present in boar seminal plasma, TGF beta(1) and TGF beta(2) were measured by immunoassay. High levels of TGF beta(1) and TGF beta(2) were detected in 100% of seminal fluid samples from 73 boars. Both were predominantly in the active, not latent form. Interferon-gamma (IFN gamma) and lipopolysaccharide (LPS), agents that interact with TGF beta signalling, were detectable in 5% and 100% of samples, respectively. TGF beta(1) and TGF beta(2) concentrations varied widely between boars, but correlated with each other and with sperm density, and remained relatively constant within individual boars over a 6-month period. Frequent semen collection substantially diminished the concentration of both TGF beta isoforms. Using retrospective breeding data for 44 boars, no correlation between TGF beta content and boar reproductive performance by artificial insemination (AI) with diluted semen was found. It is concluded that TGF beta is abundant in boar seminal plasma, leading to the speculation that, in pigs, TGF beta may be a male-female signalling agent involved in immune changes in the female reproductive tract elicited by seminal fluid.