The Forssman antigen, also known as globopentosylceramide, is a [glycolipids? glycolipid] structure formed by the addition of GalNAc? in alpha1-3 linkage to the terminal GalNAc residue of globoside. There is also evidence in the literature that Forssman-specific monoclonal antibodies can detect Forssman-reactive glycoproteins, but the nature of these molecules is not known.
The Forssman antigen molecule is expressed during embryonic and adult life in rodents and other mammals, but uncertainty exists about the ability of humans to express this antigen. For example, there is evidence that humans maintain moderate titers of naturally occurring anti-Forssman antibodies in plasma, suggesting that humans do not express the Forssman antigen. In contrast, there is evidence that such antibodies are not consistently present in humans and that when generated, may contribute to the pathogenesis of the Guillain-Barre syndrome by binding to glycolipid components of peripheral nerve myelin.
Similarly, evidence exists that small amounts of Forssman reactivity may be found on human gastrointestinal epithelium, by various human cultured cell lines, by pulmonary and gastointestinal tract carcinomas. These conflicting observations may be a reflection of varied specificities of the anti-Forssman monoclonal antibodies used by different investigators and by differences in epitope reactivity achieved with immunohistochemical procedures versus thin-layer chromatography/antibody overlay procedures. The function of this antigen is not known.
The ability of anti-Forssman antibodies to disrupt tight junction formation, apical-basal polarization, and adhesion suggests that this molecule may participate in cell-cell adhesion and communication processes. The mechanisms that account for these observations are not defined, nor are there corollary studies that have confirmed these observations in a more physiological context.