The Role of the Physical State of Lipopolysaccharides in the Interaction with Complement

Abstract

Lipopolysaccharides interact with complement onIy when they are present in a state of high aggregation with a high apparent molecular weight. Lipopolysaccharides in uniform salt forms prepared by electrodialysis and neutralization with different bases exhibited distinct differences in their anticomplementary activity which correlated with differences in their sedimentation coefficients.Conversion of smooth (S) form lipopolysaccharides into the low-molecular-weight triethylamine form completely abolished their anti-complementary activity while conversion into the highmolecular-weight sodium form increased their activity. In contrast, a similar treatment of highly defective Re and Rd rough (R) form lipopolysaccharides had no effect on their ability to interact with complement. Both the triethylamine and sodium forms were strongly anti-complementary despite large differences in their molecular weight. This was found to be due to the property of R lipopolysaccharides to reaggregate into a large-molecular-weight form through absorption of Mg2+ and Ca2+ present in the guinea pig serum used as complement source. Defective lipopolysaccharides derived from the Ra and Rb classes showed only negligible anti-complementary activity which did not increase by conversion into salt forms with high molecular weight.Many lipopolysaccharides interact with complement in vitro leading to loss of complement hemolytic activity [1,2]. This property is embedded in the lipid A part of the molecule and is expressed only by soluble lipopolysaccharides [ 2 ] . In the last years, much effort has been devoted to identifying the mechanisms underlying this interaction and much information has become available. Thus, it is known today that interaction of lipopolysaccharides with complement involves mainly the terminal complement compo-. nents, and that serum factors other than classical antibody are required [3 -51.Although lipid A is a common constituent of all lipopolysaccharides, a number of preparations exists which although soluble, do not exhibit this activity [2,6]. The inability of many lipopolysaccharides to interact with complement has drawn little attention and consequently structural or physicochemical requirements that may be prerequisite for the expression of anti-complementary activity by lipopolysaccharides have remained virtually unexplored.Lipopolysaccharides are acidic macromolecules due to the presence of phosphate, pyrophosphate and carboxyl groups in the molecule.Recently we have shown that the physical state of a lipopolysaccharide is determined by the type of basic ions that are present in salt form with acidic groups in the molecule. With the aid of electrodialysis it was possible to obtain lipopolysaccharides in defined salt forms which showed distinct differences in their molecular weight as judged by sedimentation coefficient determinations in the ultracentrifuge [7].In the present communication lipopolysaccharides in defined salt forms are employed to find out whether a relation exists between the molecular size of a ...

Investigation into the fluidity of lipopolysaccharide and free lipid A membrane systems by Fourier‐transform infrared spectroscopy and differential scanning calorimetry

“…9 shows the influence of different proton concentrations (pH variation in the range 1.6- 11.8) on the monolayer isotherms of a lipopolysaccharide R595 preparation, clearly demonstrating a reduction in the limiting area/molecule when changing from a basic to an acidic pH with the molecules then being more tightly packed. Parallel to this, the transition from the expanded to the compressed liquid phase, analogously to the P++a transition of the bilayer system, takes place at steadily decreasing pressures corresponding to an increase in the transition temperatures (see [32]). At extremely basic pH values (10.1, 11.8) this transition does not take place at all, the monolayer stays in the expanded liquid phase up to very high pressures.…”

“…Further evidence for the importance of the fluidity of the hydrophobic portion of lipopolysaccharide comes from the fact that it strongly depends on the kind of salt form, as can be seen in the Table. Galanos and Liideritz [32] investigated the anticomplementary activity of various lipopolysaccharides from Salmonella in different salt forms. The Na' salt form lipopolysaccharide gave the highest activity, decreasing in the sequence natural, ethanolamine, and triethylamine salt forms.…”

Interaction of Lipopolysaccharides With Plasma High Density Lipoprotein in Rats

“…tilled water and adjusted to pH 7.2 with triethylamine. The physicochemical and biological properties of the two LPSs were described elsewhere (14,16,18,32). '4C-labeled LPS of S. abortus-equi and S. Minnesota R595 were prepared from bacteria grown on ['4C]glucose-containing medium.…”

Evidence for Different Requirements in Physical State for the Interaction of Lipopolysaccharides with the Classical and Alternative Pathways of Complement

“…The basis for such inherent variability in the capacity of various lipopolysaccharides to interact with complement is not completely understood and probably reflects both the chemical composition of the lipopolysaccharide as well as its physical state. With respect to the latter variable, Galanos and Liideritz [5] have clearly documented the importance of molecular weight in the anticomplement activity of a variety of lipopolysaccharide preparations. In these studies they demonstrated that the conversion of smooth (S) form lipopolysaccharides to their low molecular weight triethylamine salt form results in a marked reduction of anticomplement activity, while conversion to their respective high molecular weight salt form results in enhanced activity.…”