Glycosylated Human Prolactin: Detection by Immunoblotting of Biological Fluids Is Confounded by Antisera Crossreactivity with Immunoglobulins

Glycosylated human prolactin is found in several biological fluids and can only be detected by western immunoblotting. Glycosylated prolactin migrates at 25,000-27,000 molecular weight while prolactin migrates at 23,000. We have discovered that several antihuman prolactin sera crossreact with some light chain components of human immunoglobulins, which also migrate at 25,000 on electrophoretic gels run under reducing conditions. Evidence is provided for prolactin binding to immunoglobulins in biological fluids, which may explain why some polyclonal anti-prolactin sera demonstrate this crossreactivity.