Abstract
The role of sialoglycolipids (gangliosides) as receptors for the human pathogen Mycoplasma pneumoniae was investigated by using purified gangliosides of known carbohydrate structures as inhibitors of the binding of 51Cr-labeled erythrocytes to sheet cultures of M. pneumoniae. We found that sialoglycolipids with long carbohydrate backbones of the poly-N-acetyllactosamine type were more potent inhibitors of M. pneumoniae binding than those with short carbohydrate chains. This is in accord with earlier inhibition data for glycoproteins and oligosaccharides. Thus, the inhibitory activity of a fraction of bovine erythrocyte gangliosides containing long backbone structures of I antigen type was approximately 200 times greater than that of the short chain gangliosides GM3 and GT1b. The binding of M. pneumoniae to erythrocytes of I and i antigen types was found to be comparable, indicating that M. pneumoniae in its adhesive specificity may not distinguish between the branched carbohydrate backbones of I type and the linear structures of i type. Thus, the production of autoantibodies to the backbone structures of I type rather than i type after infection with this agent may simply reflect a greater abundance of branched carbohydrate receptors of I type on the surface of host cells with which the mycoplasma forms immunogenic complexes.