ABSTRACT

Lectins are carbohydrate-binding proteins of non-immune origin which, among other functions, mediate cell-cell interactions by binding to complementary carbohydrate moieties (Sharon and Lis, 1989). Increasing structural and functional understanding of this group of proteins has led to the realization that in addition to their carbohydratebinding activity, biological functions of lectins may also be mediated by interaction with non-carbohydrate ligands (Barondes, 1988). Cell-cell interactions mediated by lectins include those between parasites and host cells (Pereira, 1986; Ward, 1996). One of the hallmarks of host-parasite interactions is specificity, which may be manifested at the level of host species, tissue site, cell type or receptor (Pereira, 1986). This selectivity suggests that specific parasite molecules and complementary ligands on host cells mediate these interactions. The specificity of lectins together with the diversity of carbohydrate residues confers these molecules with recognition and discrimination properties, which enable them to contribute to the selectivity of the host cell-parasite interaction. Interactions between parasite and host cells are complex processes, which involve multiple receptors and complementary ligands on both cell types. Examples of such interactions include recognition, adhesion, invasion, cell signaling and cytotoxicity.