Further studies on the dependence of some examples of anti-M and anti-N on the presence of red-cell-borne sialic acid.

Previous studies have shown that some examples of anti-M and anti-N fail to agglutinate neuraminidase-treated (NeuNAc-depleted) red cells. This investigation extends those observations and shows that the antibodies fail to bind to such treated red cells. These observations may mean that NeuNAc residues act to orient the protein portion of the MN sialoglycoprotein so that it is recognized by the antibodies. Alternatively, it is possible that NeuNAc residues are an integral part of the antigen defined.