[Identification of a human sperm antigen to infertile women's serum and follicular fluid with high sperm immobilizing activity].

In our previous paper, we reported a sperm coating antigen with a molecular weight of approximately 12,000 daltons from sperm membrane fraction by using rabbit anti-seminal plasma antiserum. In this paper, we isolated a human sperm antigen with the same sperm preparation by using sera of infertile women with sperm immobilizing antibody. The isolated antigen showed the following characteristics: (1) It is a glycoprotein with an affinity with lentil lectin and its molecular weight is approximately 15,000 daltons. (2) Little activity of the antigen was seen in seminal plasma. The antigen is localized on the equatorial segment of the acrosome. These facts indicate that the antigen is a genuine sperm antigen and is not a sperm coating antigen. (3) The antigen is bound with the sperm immobilizing antibody in follicular fluid of an infertile woman who has a sperm immobilizing antibody in her serum. This indicates that sperm immobilizing antibody in follicular fluid recognizes the same antigen as in the serum.