Surface properties of bloodstream Trypanosomes (Trypanosoma brucei)

The African trypanosome (Trypanosoma brucei brucei) in its bloodstream phase has been found to possess rather unique surface properties. Results of lectin and iron colloid binding studies have indicated that the parasite's surface coat is devoid of many types of exposed carbohydrate residues which commonly are expressed on a variety of mammalian cell types. These include: glucose, mannose, galactose, n-acetylglucosamine, n-acetylgalactosamine, and neuraminic acid. A number of these carbohydrates (E.G., glucose, mannose, galactose and n-acetylgalactosamine) are, however, buried within the surface coat as evidenced by lectin binding to trypsinized parasites. The surface of well preserved parasites also lack exposed sialic acid and phospholipid moieties. Moribund parasites (or trypsinzed organisms) with altered surface coats were found to possess well defined phospholipid regions, but not negatively charged sialyl residues. Results presented tend to suggest that carbohydrates and phospholipids are not present in the outermost portion of the glycocalyx, thus exerting little or no influence on surface-mediated biological activities. However, the presence of such components on the plasmalemma is presumed to be structurally significant; especially during those developmental phases where the glycocalyx is absent, i.e., fly midgut phase.