Selective interaction between lymphocytes and lipid A subunits in lipopolysaccharide macromolecular aggregates.

The interaction between bacterial lipopolysaccharides (LPS) and murine spleen cells was examined. The results indicate that lipid A-rich subunits, contained within the heterogeneous LPS macromolecule, associated selectively with spleen cells. In the LPS not associated with spleen cells, the relative amounts of lipid A-rich subunits were reduced; however, this reduction was not of a sufficient magnitude to be reflected in the stimulation of B cells. By constructing hybrid LPS macromolecules with various amounts of lipid A-rich subunits it was documented that mitogenic activity of B cells was relatively refractory to lipid A subunit composition. Furthermore, the presence of polysaccharide-rich subunits regulated downward the expression of lipid A-dependent activity.

Immune responses to hapten-lipopolysaccharide conjugates in mice. III. Genetics of the antibody response to polysaccharide antigens.

Antibody responses to the polysaccharide antigens of bacterial lipopolysaccharides and their hapten derivatives are herein documented to be under multigenic control. Among the genes responsible for the antibody response to these polysaccharide antigens include those coded for by genes located on the X chromosome and those on chromosome 17 linked to genes in the H-2 and/or Qa loci. The use of B10 congenic mice revealed that two genes on chromosome 17 are involved in the regulation of the antibody response to bacterial polysaccharide antigens. The use of CXB recombinant inbred mice confirmed the multigenic control of the antibody response within their background array of genes. The data clearly demonstrate that immune responses to these polysaccharide antigens are under genetic control, the importance of which may be of significance with regard to humoral protection during gram-negative infection.

Interaction of latex-insolubilized endotoxins with murine macrophages: phagocytic responses of endotoxin-responsive (C3HeB/FeJ) and -unresponsive (C3H/HeJ) macrophages in vitro.

Insolubilized lipopolysaccharides (LPS) were prepared by covalently coupling LPS from polysaccharide-deficient S. minnesota R595 and polysaccharide-rich E. coli 055:B5 to carboxylated latex particles. The stability of these LPS-latex complexes was determined using several assays to detect soluble LPS following incubation at ambient and elevated temperatures. Resident and thioglycollate-elicited macrophages from both LPS-responder C3HeB/FeJ and LPS nonresponder C3H/HeJ mice were examined for their capacity to phagocytose the LPS particles following in vitro culture for various time periods. Uptake was demonstrated by an increase in the number of particles within the macrophages with increasing time of incubation. Rough polysaccharide-deficient LPS-latex particles were found to be more readily phagocytosed than control particles, whereas smooth polysaccharide-rich LPS particles were phagocytosed less readily than the controls. Qualitatively similar results were found in the relative rate of uptake of particles by the macrophages from the endotoxin-responsive and -unresponsive mouse strains used in this study.

Stimulation of T-independent antibody responses by hapten-lipopolysaccharides without repeating polymeric structure.

The murine immune response to a haptenated lipopolysaccharide (LPS) lacking repeating oligosaccharide determinants was studied. The LPS was extracted from a rough strain of bacteria (Salmonella minnesota R595) and chemically haptenated with either trinitrophenol or fluorescein isothiocyanate. These preparations of hapten-R595 LPS were shown to be immunogenic. Furthermore, the immune response to the hapten was demonstrated to occur independent of T cells and was not merely the result of enhanced polyclonal B-cell activation. The capacity of such hapten-LPS conjugates without repeating polymeric structures to stimulate T-independent antibody responses provides information on the molecular requirements for the activation of murine B lymphocytes.