Human Natural Antibodies Recognizing Glycan Galβ1-3GlcNAc (LeC)

Abstract

The level of human natural antibodies of immunoglobulin M isotype against LeC in patients with breast cancer is lower than in healthy women. The epitope specificity of these antibodies has been characterized using a printed glycan array and enzyme-linked immunosorbent assay (ELISA), the antibodies being isolated from donors’ blood using LeC-Sepharose (LeC is Galβ1-3GlcNAcβ). The isolated antibodies recognize the disaccharide but do not bind to glycans terminated with LeC, which implies the impossibility of binding to regular glycoproteins of non-malignant cells. The avidity (as dissociation constant value) of antibodies probed with a multivalent disaccharide is 10−9 M; the nanomolar level indicates that the concentration is sufficient for physiological binding to the cognate antigen. Testing of several breast cancer cell lines showed the strongest binding to ZR 75-1. Interestingly, only 7% of the cells were positive in a monolayer with a low density, increasing up to 96% at highest density. The enhanced interaction (instead of the expected inhibition) of antibodies with ZR 75-1 cells in the presence of Galβ1-3GlcNAcβ disaccharide, indicates that the target epitope of anti-LeC antibodies is a molecular pattern with a carbohydrate constituent rather than a glycan.

Repertoire of glycan‐binding placenta‐associated antibodies in healthy pregnancy and in pre‐eclampsia

“…Only class G antibodies were eluted from the placenta, while IgMs were absent (IgAs were not investigated); this observation is in line with the previously published data, [39][40][41] however, in few studies, certain amounts of IgM and IgA were found in addition to predominant IgG. 42 Functional activity of IgG antibodies from healthy human placenta has been studied.…”

Antibodies as Biosensors’ Key Components: State-of-the-Art in Russia 2020–2021

“…The epitope specificity of these antibodies was characterized using a printed glycan array and enzyme immunoassay; the antibodies recognized a disaccharide but did not bind to glycans ending in Le C , which implies that it is impossible to bind to ordinary glycoproteins of non-malignant cells. The antibodies had a cytotoxic effect on breast cancer cells, which suggests that anti-Le C plays a role in tumor surveillance [106].…”

Glycosylation Alterations in Cancer Cells, Prognostic Value of Glycan Biomarkers and Their Potential as Novel Therapeutic Targets in Breast Cancer

“…A number of studies show that the disaccharide LeC is a potential biomarker, as patients with BC have lower levels of nAbs (natural antibodies) of immunoglobulin M against LeC compared to healthy patients. These studies suggest that anti-LeC nAbs are involved in cancer surveillance and are believed to be cytotoxic to cancer tissues [ 48 ].…”