Isolation and serological characterization of a monoclonal antibody recognizing the N blood group antigen

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Abstract
A mouse hybridoma was isolated which secretes a hemagglutinating monoclonal antibody (MoAb) recognizing the N and N blood group antigens. All human red cells expressing either N or one of the alleles of Ss (i.e. N) were strongly agglutinated by the MoAb diluted 4-fold. The only cells not reactive were of the M+N-S-s-(U-) and M-N-S-s-(U+) phenotype and cells expressing Lepore-type hybrids of the MN and Ss sialoglycoproteins, which do not express N or N. Red cells of the N+S-s-(U-) phenotype were rendered unreactive to MoAb following treatment of the cells with trypsin, which is known to destroy N antigen activity. Cells expressing S and/or s maintained their reactivity with MoAb following trypsin treatment, which does not cleave N from the Ss sialoglycoprotein. When spent culture medium containing MoAb was diluted and tested against a panel of red cells, the antibody titer fell into 2 distinct categories depending upon the MNSs phenotype of the target. Red cells expressing either homozygous or heterozygous N-sialoglycoprotein (N-SGP) were agglutinated by 128-fold diluted MoAb. In contrast, a 16-fold dilution of MoAb was the endpoint for agglutination of cells lacking N-SGP, but expressing S and/or s.