Antigens cell surface sialic acid masking

Whereas for a long time the main function of terminal sialic acid residues was considered as a mask for recognition sites on cell surfaces, e.g. galactose residues or antigens as outlined above, it is only in the last few years that receptors have been described which connect the structural diversity of sialylated glycoconjugates to specific functions in cellular interactions. 

The role played by sialic acid in masking cell-surface antigens may be ascertained only by the enhanced antigenicity created by its removal from the cell surface. Masking was first noted by Thomsen (1927) in the study of the erythrocyte. In a phenomenon which came to be known as the Thomsen effect, Friedenreich (1930) observed the agglutination of red blood cells under the influence of a substance later shown to be the... 

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