IDENTIFICATION OF HUMAN SEMINAL PLASMA COMPONENTS THAT BIND IGG(2) VARIANT

Human seminal plasma (hsp) contains soluble proteins capable of binding immunoglobulin (Ig) G. Two novel components with estimated molecular sizes of 90 and 21 kD interact specifically with a variant of IgG(2) found in 20% of human sera tested. The common IgG(2) present in human sera and other subclasses of IgG did not bind with the hsp components. The present finding shows that the interacting IgG(2) is a variant and not the common or prevalent species. The 90-kD component of hsp with IgG(2) binding property is probably a nonglycosylated protein, whereas the 21-kD component is a glycosylated protein. The 90- and 21-kD components were detected in 20% of hsp specimens tested. Thus they are not present in the majority of hsp. Since the IgG(2) binding components of hsp and the serum IgG(2) variant are found in 20% of men and 20% of individuals, respectively, they can be used as genetic markers.