Glycans have been known to pose serious challenges to antibody development. They are usually not (or only weakly) immunogenic, and they cannot be processed by antigen-presenting cells to create a T-helper response. Therefore, carbohydrate-specific antibodies normally arise, if at all, only as low affinity IgMs.
Recently, however, new technologies have been developed that allow generation of high-affinity IgG type antibodies to complex glycans. These involve chemoenzymatic synthesis of glycan substructures in conjunction with novel immunogenic carrier proteins or peptides and immunization of transgenic mice that are missing the gene encoding one or the other glycosyl transferase enzyme required for biosynthesis of the glycan of interest.
Antibody Solutions has developed antibody-secreting clones that are specific for the glycosylated versus the naked form of a peptide (shown in the adjacent figure). We have also custom-made a rabbit antiserum that recognizes terminal N-acetylglucosamine 6-sulfate and does not bind significantly to unsulfated N-acetylglucosamine.
For the same group of researchers we also made a large quantities of a monoclonal IgM known as MECA-79 that is specific to a sulfated N-acetyllactosamine epitope on sulfoadhesin, a family of complex glycans implicated in chronic inflammatory diseases. This antibody is commonly used in small quantities for immunohistochemistry of inflamed lesions in human and animal models. However, the authors needed gram quantities for an in vivo study in sheep, which Antibody Solutions provided rapidly and cost-effectively (Abraham et al., 2005).