Significance of carbohydrate components of cell surfaces

This article is focused on a family of carbohydrate structures which are (a) target antigens of autoantibodies and (b) onco-developmental antigens which change during embryonic development, cell differentiation, maturation and oncogenesis. Among the carrier molecules of these saccharide structures is the receptor for epidermal growth factor. Perturbation of these structures on the isolated receptor enhances autophosphorylation of the receptor glycoprotein. This suggests that the carbohydrate chains may be part of a growth regulatory network which may be 'tuned' or perturbed via interactions with endogenous lectins or by adhesins of infective agents. Certain sialylated forms of these oligosaccharide structures serve as receptors for a pathogen of man, Mycoplasma pneumoniae which, following infection, elicits anti-erythrocyte autoantibodies. These autoantibodies are directed against the backbone domain of the carbohydrate receptor and are therefore anti-receptor antibodies. These observations suggest that complex formation between the adhesins of infective agents and specific saccharides of host-cell membranes may be a 'new' mechanism for eliciting autoantibodies.