Identification of Human Seminal Plasma Components that Bind I_gG₂Variant

Abstract

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 IgG2 found in 20% of human sera tested. The common IgG2 present in human sera and other subclasses of IgG did not bind with the hsp components. The present findings shows that the interacting IgG2 is a variant and not the common or prevalent species. The 90-kD component of hsp with IgG2 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 IgG2 binding components of hsp and the serum IgG2 variant are found in 20% of men and 20% of individuals, respectively, they can be used as genetic markers.