Human seminal plasma contains a component that binds immunoglobulins (
Ig). The Ig binding factor was purified by ammonium sulphate precipita
tion, preparative isoelectrofocusing and gel filtration chromatography
and found to bind strongly human IgGl and mouse IgM. This seminal pla
sma component may possess immunosuppressive activity and may modulate
the activities of the immunosurveillance system of the reproductive tr
act.