Antibodies to Acholeplasma laidlawii membrane lipids in normal guinea pig serum

Abstract

Acholeplasma laidlawii is killed and lysed by fresh normal guinea pig serum (GPS) without additional antibodies. Prior incubation of GPS with whole A. laidlawii organisms abolishes the killing activity of GPS. In the present study it was demonstrated that antibodies are present in normal GPS. The classical pathway, not the alternative pathway, of the complement sequence was activated by these antibodies in fresh normal GPS. The antibodies in GPS belong to the IgG class of immunoglobulins. They are directed predominantly against the membrane phospholipids ofA. laidlawii. These antibodies may be induced either by natural infection of guinea pigs with A. laidlawii or by antigenic determinants of other microorganisms or food antigens.In recent years it has been clearly demonstrated that some mycoplasmas are killed and lysed by the combined action of antibodies and complement (1,6,8,12,15,20,24,25,34). Fresh normal guinea pig serum (GPS) has been most frequently used as the source of complement in these experiments. In studies on immune lysis of Mycoplasma pneumoniae it was noted that GPS by itself, without addition of antibodies, reduced the number of viable organisms. As had been reported by Gale and Kenny (15), Sethi and Teschner (34), and from our laboratory (8), removal of the growth-inhibitory substances from GPS by absorption with killed M. pneumoniae was not possible. Nevertheless, the possibility that small amounts of antibodies to M. pneumoniae, not detectable by our methods, were present in normal GPS could not be excluded.It has been recently shown by Bredt and Bitter-Suermann (4) that M. pneumoniae can activate the guinea pig complement system via the altemnative pathway. This activation results in rounding of the organisms. Efficient killing requires, in addition, the entire complement sequence. It was also shown that M. pneumoniae can interact directly with Cl in the absence of detectable amounts of antibodies (5).We have previously demonstrated that a decrease in viability of Acholeplasma laidlawii occurs when the organisms are incubated with fresh GPS (11). In this publication, data are pret Present address: sented indicating that antibodies of the immunoglobulin G (IgG) class can be detected in normal GPS. These antibodies are directed against the membrane lipids of the organisms and activate preferentially the classical pathway of complement.(These results were presented in a preliminary form at the Annual Meeting of the American Society for Microbiology, New York, 1975, and the Arbeitstagung der Deutschen Gesellschaft ftir Hygiene und Mikrobiologie, Mainz, West Germany, 1976).MATERIALS AND METHODS Organisms and growth media. A. laidlawii, oral strain, and M. pneumoniae, strain PI 1428, originally obtained from R. M. Chanock, Bethesda, Md., were used. A. laidlawii had been subcultured several times on artificial medium. M. pneumoniae was used in its sixth passage on growth medium (9,11).The medium for A. laidlawii consisted of 350 ml of PPLO broth (Difco Laboratories, Detroit, Mich.) supplemented wi...

Immune electron microscopy of cross-reactions between Mycoplasma pneumoniae and human erythrocytes

“…It is tempting to speculate that these changes in reactivity of the mycoplasmal membrane may have a common ground in the glycocalyx material which, by fixation, is rendered less sticky for proteins in solution or on the surface of erythrocytes. However, it is also possible that the nonspecific staining may have a basis analogous to that of natural antibody in guinea pig sera with A. laidlawii membrane lipids (4). Glutaraldehyde fixation decreases the mobility of membrane proteins by mutual cross-linking, thereby preventing the access of antibody to any nonspecifically reactive components.…”