From a Men’s Health Science Newsgroup on male infertility:
Although autoimmunization to spermatozoa is a cause of male infertility, the cause of antibody formation is unknown in most cases. It has been shown that the titer is usually unchanged for as much as 16 years in the same individual. Trials to reduce the titer with varying methods have not been successful. A new possibility of treatment was indicated by the finding of a higher incidence of prostatitis in men with sperm antibodies than in a control group. Following treatment of prostatitis we observed a reduction of the antibody titer in eight cases. In five cases the cervical mucus penetrating capacity of the spermatozoa improved, and conception occurred.
To make this clearer. They are simply stating that it would seem prostatitis starts much earlier than is usually suspected or known and that treating men for prostatitis early on would help with male infertility associated with weak mucus penetrating capabilities.