Immunological analysis of glycolipids and lipopolysaccharides derived from various mycoplasmas

The lipids and lipopolysaccharides of five mycoplasmas were examined for complement-fixing activity to antimembrane rabbit sera. Total glycolipid fractions and the aqueous phenol fractions (lipopolysaccharides) from the membranes of Acholeplasma laidlawii, A. modicum, A. axanthum, and Mycoplasma neurolyticum exhibited significant antigenic activity. The glycolipids and phosphoglycolipids from Thermoplasma acidophilum were either anticomplementary or did not react due to their extreme hydrophobic nature. High activity was found using the lipopolysaccharide of T. acidophilum. The pure glycolipids and phosphoglycolipids of the Acholeplasma and Mycoplasma species also exhibited significant complement-fixing activity. Acylation of the sugar residues of these lipids reduced or negated complement-fixing activity. Double cross-reactions between the glycolipids of A. laidlawii and A. modicum appeared to be due to mono- and diglucosyl diglycerides of identical structure. Specificity of glycolipid structure was noted by the absence of cross-reactions between A. laidlawii and M. neurolyticum, the glycolipids of which differ only in the nature of the glucose linkages. The existence of lipopolysaccharides in the membranes of mycoplasmas and their complement-fixing activity in the presence of antimembrane sera suggest their possible importance as specific antigenic determinants.