title: LPS regulation of the immune response: Bacteroides endotoxin induces mitogenic, polyclonal, and antibody responses in classical LPS responsive but not C3H/HeJ mice.
abstract: Recent studies have suggested that lipopolysaccharide (LPS) derived from gram-negative organisms such as Bacteroides, which are not members of the Enterobacteriaceae, stimulate B cells from the classic LPS-hyporesponsive C3H/HeJ mouse. In the present study, purified, phenol-water-extracted LPS from Bacteroides fragilis ATCC 25285 (B-LPS) was tested for its ability to induce in vivo and in vitro responses in classic LPS-responsive C3H/HeN, LPS-hyporesponsive C3H/HeJ, and (C3H/HeN X C3H/HeJ)F1 hybrid mice. B-LPS induced mitogenic responses in both C3H/HeN and C3H/HeJ spleen cell cultures when cells were cultured under standard conditions, i.e., 8 X 10(5) cells/well. Interestingly, when lower spleen cell numbers were tested with B-LPS, a typical responsive-nonresponsive pattern developed in which good mitogenic responses were induced by B-LPS in C3H/HeN cultures and in which low responses in C3H/HeJ spleen cell cultures were evident. In vivo immunization of mice with B-LPS resulted in high antibody responses in C3H/HeN, intermediate responses in F1, and low responses in C3H/HeJ mice. When purified splenic B cells were incubated with B-LPS, both mitogenic responses and polyclonal immunoglobulin M (IgM) synthesis occurred in C3H/HeN cultures, whereas intermediate responses were noted in F1 cultures and no response was seen in B cell cultures from C3H/HeJ mice. Furthermore, in vitro TNP-B-LPS responses were induced in C3H/HeN spleen cells or purified B cell cultures, and intermediate anti-TNP PFC responses occurred in F1 spleen cells or purified B cell cultures. The toxicity of B-LPS was tested in galactosamine-sensitized mice. The LD50 values for B-LPS in classic LPS-responsive C3H/HeN and C57BL/6J mice were 0.6 microgram and 1.1 microgram, respectively; F1 hybrid mice were approximately 15-fold more resistant, whereas C3H/HeJ mice gave an LD50 of 1650 micrograms. This study shows that phenol-water preparations of B-LPS are biologically active and induce responses in the classic LPS-responsive but not in the LPS-hyporesponsive C3H/HeJ mouse strain.
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis*; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D001441:Bacteroides fragilis / Q000276:immunology*; D004731:Endotoxins / Q000494:pharmacology; D007075:Immunoglobulin M / Q000096:biosynthesis; D007928:Lethal Dose 50; D008070:Lipopolysaccharides / Q000494:pharmacology* / Q000633:toxicity; D008213:Lymphocyte Activation; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D014301:Trinitrobenzenes / Q000276:immunology; D000511:alpha-Macroglobulins / Q000494:pharmacology*
chemical_list: D000907:Antibodies, Bacterial; D004731:Endotoxins; D007075:Immunoglobulin M; D008070:Lipopolysaccharides; D014301:Trinitrobenzenes; D000511:alpha-Macroglobulins; C032306:polyclonal B cell activator