Interaction of Mycoplasma pneumoniae with human lung fibroblasts: role of receptor sites.

The biochemical nature of the neuraminidase-sensitive Mycoplasma pneumoniae receptor site on human lung fibroblast cells was studied. Purified, mixed sialoglycolipid (ganglioside) preparations from human and bovine tissues did not bind to M. pneumoniae organisms and block their subsequent attachment to fibroblasts. Fibroblasts incubated for 24 h in sialoglycolipid solutions to increase the ganglioside content of their membranes did not show increased pathogen attachment when later incubated with mycoplasmas. HeLa cells grown in the presence of sodium butyrate to increase GM3 ganglioside levels likewise did not have significantly increased uptake of M. pneumoniae organisms. Treatment of fibroblasts with enzymes indicated that the mycoplasma receptor site is trypsin and papain resistant but Pronase sensitive. Pronase digests of fibroblast membranes contained a product(s) which combined with M. pneumoniae cellls and cosedimented with them during centrifugation. Glycoproteins, purified from fibroblast membranes by a lithium diiodosalicylate solubilization technique, similarly bound to M. pneumoniae organisms. Collectively, these data suggest that the major component of the M. pneumoniae receptor site is a sialoglycoprotein with little or no lipid.