Antibody recognition, carbohydrate structures

The effector function of an antibody is defined as the mediation of other host-defense mechanism besides antigen recognition. It is highly determined by the carbohydrate structure of the heavy chain. 

Taken together, these results suggest that molecular recognition of the dodecapeptide by antibodies differs from its recognition by concanavahn A, and that the immunological cross-reactivity observed in some studies does not reflect structural mimicry. That molecular recognition by concanavalin A of carbohydrates and peptides differs has also been shown in structural studies. Here, the functional molecular mimicry observed with respect to different receptors should not be assumed to imply structural mimicry—the inter-molecular interactions may differ in each case. 

This biosensor consists of two surface-tethered components. The biorecognition element can be an antibody (Section 19-5), DNA, RNA, or carbohydrate with specific affinity for analyte. A structural analog of the analyte is bound to a flexible arm adjacent to the recognition element. In the absence of analyte, the tethered analog binds to the recognition element. 

This volume contains the papers presented in a symposium on carbohydrate-protein interaction. The symposium was devoted to an exploration of protein-glycoconjugate interaction in a wide range of biological phenomena the interaction of enzymes, antibodies, and lectins with complementary carbohydrate molecules the recognition of carbohydrate-containing structures by chemoreceptors such as taste and other plasma membrane proteins and the role of carbohydrates in the organization of connective tissue. 

Nevertheless, the potential for autoimmune disease would clearly exist if one considers the polyspecificity of immune recognition molecules such as B cell receptors, antibodies, T cell receptors and MHC molecules. Further, the polyspecificity of immune receptors is also able to transcend the biochemically defined classes of biomolecules. For instance, the monoclonal antibody SYA/J6 has been demonstrated to have a dual specificity, binding a specific carbohydrate or a specific peptide with comparable affinity.68 Detailed analysis of the interatomic interactions between the antibody combining site and either the carbohydrate or the peptide antigens demonstrated that functional mimicry is possible without exact structural mimicry. This example underlines the case that it is not possible to predict with certainty whether the molecular surfaces of all potentially cross-reactive epitopes, whether of foreign or self molecules, will, or will not, be able to bind to a specific antibody. 

Figure 1 Characteristic carbohydrate moieties serve as markers for biological recognition. Af-Glycan type II chains (Gaipi 4GlcNAc) in the tri-antennary cluster configurations with (Tri-II) and without sialic acid terminal residues (asialo-Tri-II). The asialo-Tri-II sugar moieties but not the Tri-II structures are specifically targeted by a horse-neutralization antibody of SARS-CoV (68).

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