Cellular mechanism of endotoxin unresponsiveness in C3H/HeJ mice.

B cells from C3H/HeJ mice fail to respond to an endotoxin (LPS K235) which is mitogenic for normal mice including the closely related C3H/HeN strain. The cellular basis for this unresponsive state has been investigated. The C3H/HeJ mice have normal numbers of B cells, which are capable of normal responses to other B cell mitogens, such as polyinosinic acid (Poly I). Addition of normal macrophages or spleen cells fails to reconstitute the normal response. Furthermore, neither macrophages nor spleen cells from the C3H/HeJ strain suppress the normal C3H/HeN spleen cells. Finally, spleen cells enriched for B cells by the removal of macrophages or T cells demonstrate the same differences in responsiveness to LPS. These results indicate that LPS unresponsiveness is a defect of the B cell itself and not due to suppressor cells or the absence of helper cells. When LPS is added to Poly I-stimulated cultures, there is additional enhancement of the response of normal C3H/HeN spleen cells. However, LPS causes a dose-dependent suppression of the Poly I response of C3H/HeJ spleen cells. This suppression is dependent on the time of addition of LPS to the Poly I-stimulated cultures. These data are interpreted as indicating that the binding of LPS to the membrane of C3H/HeJ B cells results in their inactivation or suppression, and that this is the basis of LPS unresponsiveness in this mouse strain.     

Genetic and biochemical evidence for the involvement of a bacterial component in the mitogenic properties of polyribonucleotides on murine B lymphocytes.

The mitogenic response of C3H/HeJ mice to the B cell mitogens, poly C and poly I, is approximately one-half the response measured in various LPS-responder strains. C3H/HeJ mice respond normally to poly I:C, the heteroduplex polymer. The low responder phenotype of C3H/HeJ mice to poly C and poly I is shown by an analysis of (C3H/HeJ x C57BL/6J-By-Ps)F1 X C3H/HeJ backcross progeny to result from a gene locus that is closely linked or identical to the defective LPS response locus expressed by the C3H/HeJ strain. The entire mitogenic activity in poly C preparations and most of the mitogenic activity in poly I preparations is insensitive to ribonuclease degradation. Hot aqueous phenol extraction of the polynucleotides separates the majority of the mitogenic activity that is soluble in the combined interface and phenol phase fraction from the aqueous soluble polynucleotides. The ribonuclease-insensitive, phenolsoluble contaminant elicits a reduced response in C3H/HeJ mice as compared to an LPS responder strain. We conclude that 1) poly C has no inherent mitogenic activity; 2) poly I preparations contain both ribonucleasesensitive and insensitive mitogenic activities; 3) the ribonuclease-resistant mitogenic activity in polynucleotide preparations has properties unlike those of LPS or lipid A; and 4) the product of LPS response gene has an effect upon the mitogenic stimulation of spleen cells by the contaminant.     

Macrophage stimulation by bacterial lipopolysaccharides. III. Selective unresponsiveness of C3H/HeJ macrophages to the lipid A differentiation signal.

Peritoneal macrophages from the endotoxin-unresponsive C3H/HeJ substrain of mice were entirely refractory to activation in vitro by protein-free LPS, a defect that was not overcome by co-culture of spleen cells from the responder C3H/St substrain with LPS resistant C3H/HeJ macrophages. The defect in responsiveness appears confined to the lipid A activation signal since C3H/HeJ macrophages were fully activated after in vitro treatment by lipid A protein (LAP)--LPS complex, isolated LAP, and BCG. Moreover, after exposure to allogeneic tumor cells in vivo, C3H/HeJ macrophages were cytotoxic for tumor target cells in vitro. By contrast, macrophages from the responder C3H/St strain were fully activated by protein-free LPS to become cytolytic for tumor cells in vitro. C3H/HeJ macrophages, therefore, exhibit a highly selective defect characterized by unresponsiveness to the lipid A activation signal of protein-free LPS and resistance to the toxic effects of high concentrations of LPS that were lethal to the responder C3H/St strain.     

Induction of phenotypic lymphocyte differentiation in LPS unresponsive mice by an LPS-induced serum factor and by lipid A-associated protein.

Spleen cells from C3H/HeJ mice are known to be unresponsive to mitogenic stimulation by LPS. We show here that T and B cell precursors of C3H/HeJ mice are unresponsive to induction of differentiation by LPS. Phenotypic differentiation of C3H/HeJ lymphocytes can be induced with DB-cAMP, Lipid A-associated protein, and with a serum factor induced by LPS in LPS responder strains.     

Defective helper T-cell activity in LPS-unresponsive C3H/HeJ mice

C3H/HeJ mice, unresponsive to LPS, exhibit a defective ability to mount antibody responses to T-dependent immunogens. The anti-TNP antibody response to TNP-HRBC, a T-dependent immunogen, was found to be lower in these mice as compared to LPS-responsive C3H/HeN mice, whereas the anti-TNP antibody response to TNP-Ficoll, a T-independent immunogen, was of the same magnitude in C3H/HeJ and C3H/HeN mice. An impaired helper activity of C3H/HeJ HRBC-primed spleen cells was demonstrated in a titration assay in which graded numbers of C3H/HeJ or C3H/HeN HRBC-primed spleen cells were added to cultures containing a constant number of unprimed spleen cells from either C3H/HeJ or C3H/HeN mice and the immunogen TNP-HRBC. The reduced helper T-cell activity of C3H/HeJ HRBC-primed spleen cells appears to be independent of macrophage defects, since C3H/HeJ and C3H/HeN macrophages were found equally effective in antigen presentation as evaluated by an in vitro antigen-specific T-cell proliferation assay. The difference in helper T-cell activity between these two substrains probably reflects a lower number and/or proliferation rate of antigen-responsive T cells in C3H/HeJ mice.     

Mitogenic activity of Actinomyces viscosus. I. Effects on murine B and T lymphocytes, and partial characterization.

Actinomyces viscosus homogenate (AVIS) contins substance(s) which cause spleen cells from conventional and germfree mice to undergo increased DNA synthesis. This mitogenic effect is primarily on B cells since spleen cells from nude mice or T-depleted spleen cells from conventional mice respond as strongly as conventional (T + B) spleen cells. Mouse thymocytes do not respond mitogenically to AVIS. It is unlikely that the mitogenic acitivity is due to the presence of LPS, since A. viscosus is Gram-positive and is not known to have an LPS cell wall component. Also, AVIS is not inactivated by polymyxin B, as are some preparations of LPS, and C3H/HeJ mouse splenocytes respond strongly to AVIS but not to LPS. The activity is heat stable, is not lost upon dialysis, and is not affected by lysozyme. Mitogenic activity is partially lost when AVIS is digested with nonspecific bacterial protease or treated with metaperiodate. Sodium hydroxide treatment completely abolishes mitogenic activity. Actinomycotic lesions are characterized by a long-tern inflammatory response involving a dense plasma cell infiltrate. We suggest that B cell mitogens form Actinomyces may play a role in the elicitation of the plasma cell component of these lesions.     

Serological properties and immunobiological activities of lipopolysaccharides from black-pigmented and related oral Bacteroides species

Lipopolysaccharides (LPS) from five species of oral Bacteroides, B. gingivalis strains 381 and ATCC 33277, B. oralis ATCC 33269, B. loescheii ATCC 15930, B. intermedius ATCC 25611 and B. corporis ATCC 33547, were extracted from whole cells by the phenol/water procedure, and subsequently purified by treatment with nuclease and ultracentrifugation. The LPS were composed of hexoses, glucosamine, fatty acids and phosphorus. Heptose and 2-keto-3-deoxyoctonate were not detected. The LPS preparations from B. gingivalis strains 381 and ATCC 33277 presented very similar SDS-polyacrylamide gel electrophoresis patterns when stained with ammoniacal silver. They produced a fused precipitin band against an antiserum to B. gingivalis 381 LPS in immunodiffusion tests. Antisera raised against the LPS from B. loescheii and B. intermedius reacted with the LPS prepared from all the oral Bacteroides strains except those of B. gingivalis. All the LPS preparations were mitogenic for spleen cells of BALB/c (nu/nu) mice, but not for thymus cells from C3H/HeN mice. The LPS induced marked mitogenic responses and polyclonal B cell activation for spleen cells of not only C3H/HeN (LPS responder) mice, but also C3H/HeJ (LPS nonresponder) mice. The mitogenic responses were not suppressed significantly upon addition of polymyxin B to the reaction mixture. These LPS also enhanced interleukin-1 production by murine peritoneal macrophages and mouse cell line J744. 1 macrophages. Hydrolysis of B. gingivalis ATCC 33277 LPS in 1 m-HCl at 100 degrees C for 1 h yielded lipid and polysaccharide. The lipid portion was largely composed of fatty acids and glucosamine, and was mitogenic for spleen cells from C3H/HeJ as well as C3H/HeN mice, while the polysaccharide portion induced no significant mitogenic responses under similar experimental conditions.     

Dysfunction of thymocytes of C3H/HeJ mice in blastogenic response to anti-thymocyte serum in vitro and its repair with lipopolysaccharide induced mediator.

In vitro mitogenic responses of thymocytes to rabbit anti-mouse thymocyte serum (ATS) have been compared in several mouse strains. The response of thymocytes of C3H/HeJ mice is about one-third of those of thymocytes of C3H/He, ATL or ATH strains. Phenol-extracted bacterial lipopolysaccharide (LPS) does not induce mitogenic response in cultured C3H/HeJ spleen cells, but the spleen cells of all other strains used are capable of responding to LPS. The low response of C3H/HeJ thymocytes to ATS is restored by adding “endotoxin soup” prepared from spleen cell cultures of LPS-responder mice in the presence of LPS. Neither soup prepared from C3H/HeJ spleen cell cultures without the addition of LPS nor soup prepared from cell cultures with LPS show such restoration of the response of C3H/HeJ thymocytes to ATS. The molecular size of the active factor in “endotoxin soup” was estimated on a Sepharose CL-4B column and determined to be about 20,000 daltons. The activity of “endotoxin soup” is destroyed by heating at 70 C for 30 min or 80 C for 10 min and diminished by digestion with trypsin. The mechanisms of restoration of low response of C3H/HeJ thymocytes to ATS by “endotoxin soup” are discussed.     

LPS regulation of the immune response: separate mechanisms for murine B cell activation by lipid A (direct) and polysaccharide (macrophage-dependent) derived from Bacteroides LPS

Lipopolysaccharide (LPS) derived from Bacteroides fragilis has been reported to stimulate mitogenic responses in spleen cell cultures from the classical LPS-hyporesponsive C3H/HeJ mouse strain; however, we have shown that purified splenic B cells from C3H/HeJ mice are hyporesponsive to phenol-water extracted LPS from B. fragilis ATCC 25285 (B-LPS). In the present study, B-LPS and its purified lipid A and polysaccharide components were tested for their ability to induce mitogenic and polyclonal IgM synthesis in spleen cell and purified splenic B cell cultures from classical LPS-responsive and -hyporesponsive mice. Mitogenic responses to B-LPS and E. coli K235 LPS(Ph) of whole spleen cells (2 X 10(5) cells/culture) or purified B cells (5 X 10(5) cells/culture) from classical LPS-responsive mouse strains (C3H/HeN, BALB/c, C57BL/6J, C57BL/10Sn, and DBA/2), F1 mice (derived from crosses between LPS responsive and C3H/HeJ mice), and classical LPS-hyporesponsive mice (C3H/HeJ and C57BL/10ScN) were high, intermediate, and low, respectively. When a higher number of whole spleen cells (5 X 10(5) cells/well) were cultured, B-LPS induced high mitogenic responses in C3H/HeN, intermediate responses in F1, and lower but significant responses in C3H/HeJ cultures. Similar results were obtained when polyclonal IgM synthesis was assessed in cultures containing 1 X 10(6) cells/culture. In contrast, the purified lipid A component of B-LPS failed to induce mitogenic responses in either whole spleen or purified B cell cultures. The addition of purified splenic B cells from C3H/HeJ mice to C3H/HeN or C3H/HeJ splenic adherent cells resulted in mitogenic responses to B-LPS, implying that the hyporesponsiveness to B-LPS seen in whole spleen cell cultures from C3H/HeJ mice at the lower cell concentration was due to limiting numbers of M phi. When splenic B cells and M phi from either C3H/HeN or C3H/HeJ mice were incubated with the lipid A or the polysaccharide moiety of B-LPS, lipid A induced mitogenic responses only in C3H/HeN cultures, whereas the polysaccharide moiety induced similar responses in both C3H/HeN and C3H/HeJ cultures. These results suggest that Bacteroides lipid A does not stimulate B cells from the classical LPS-hyporesponsive C3H/HeJ mouse strain, whereas the polysaccharide moiety of B-LPS is biologically active and mediates B cell stimulation via M phi.     

Immunobiological properties of lipopolysaccharides isolated from Fusobacterium nucleatum and F. necrophorum

Lipopolysaccharides (LPSs) were isolated from Fusobacterium nucleatum ATCC 10953 and F. necrophorum ATCC 25286 by the hot phenol/water procedure. F. nucleatum LPS was composed of 16% (w/w) carbohydrate, 10% (w/w) hexosamine and 40% (w/w) fatty acid, while F. necrophorum LPS was composed of 26% (w/w) carbohydrate, 12% (w/w) hexosamine and 28% (w/w) fatty acid. These LPS preparations induced mitogenic responses in spleen cells of BALB/c, BALB/c (nu/nu) and C3H/HeN mice, and these responses were suppressed by the addition of polymyxin B. The preparations also induced the polyclonal responses of C3H/HeN spleen cells. In addition, enhanced glucose utilization and interleukin-1 production by murine peritoneal macrophages were demonstrated. Neither spleen cells nor macrophages from the 'LPS-nonresponsive' C3H/HeJ mouse were activated by LPSs from the Fusobacterium species.     

LPS regulation of the immune response: Bacteroides endotoxin induces mitogenic, polyclonal, and antibody responses in classical LPS responsive but not C3H/HeJ mice

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.     

Modulation of Immune Response by Bacterial Lipopolysaccharide (LPS): Roles of Macrophages and T Cells in In Vitro Adjuvant Effect of LPS on Antibody Response to T Cell-Dependent and T Cell-Independent Antigens

The roles of macrophages and T cells in the adjuvant effect of lipopolysaccharide (LPS) were studied. In vitro anti-trinitrophenyl (anti-TNP) antibody responses to TNP-Ficoll and TNP-keyhole limpet hemocyanine (TNP-KLH) in spleen cells of C57BL/6 mice showed the most enhancement, when LPS was added to cultures at 1 μg/ml 48 hr after culture was started. The responses to these antigens were enhanced markedly by LPS in whole and macrophage-depleted spleen cells. The enhancement was greater in the latter group than in the former. The adjuvant effect among whole, T cell-depleted, macrophage-depleted and both macrophage- and T cell-depleted spleen cells was compared. The response to TNP-Ficoll was enhanced markedly by LPS in all groups. The enhancement was greater in the latter two groups than in the first two groups. The response to TNP-KLH was enhanced by LPS strongly in macrophage-depleted spleen cells, moderately in whole and both macrophage- and T cell-depleted spleen cells, and only slightly in T cell-depleted spleen cells. Enhancement was restored to T cell-depleted spleen cells by adding T cells. The response to TNP-KLH of macrophage-depleted spleen cells of LPS-responsive C3H/HeN mice which was enhanced by LPS was suppressed by adding splenic macrophages of C3H/HeN mice, but not of LPS-nonresponsive C3H/HeJ mice. The response to TNP-KLH of macrophage-depleted spleen cells of C3H/HeJ mice was not enhanced by LPS, irrespective of the addition of macrophages of C3H/HeN mice. The results indicate that B cells are activated directly by LPS, and T cells enhance and macrophages suppress the adjuvant effect of LPS.     

Lack of responsiveness of C3H/HeJ macrophages to lipopolysaccharide: the cellular basis of LPS-stimulated metabolism.

The rate of glucose utilization has been used as a measure of LPS-induced activation of cultures of C3H/HeN and C3H/HeJ spleen cells, peritoneal cells, and purified peritoneal adherent cells. Peritoneal cells utilized 40 to 60 times more glucose than did spleen cells and purified adherent monolayers were more active than mixed peritoneal cells, suggesting that only macrophage metabolism was being measured. The cell preparations for C3H/HeJ mice were not activated by Escherichia coli K235 LPS prepared by extensive phenol extraction, whereas C3H/HeN cells were activated by the LPS. Cells from both strains were activated by a commercially obtained E. coli 0111:B4 LPS and butanol-extracted K235 LPS. The addition of 10% C3H/HeN spleen cells to C3H/HeJ peritoneal cells resulted in a marked enhancement of glucose utilization. These findings suggest that LPS-induced enhancement of macrophage metabolism occurs both by direct action of LPS on macrophages as well as indirectly through activated lymphocytes.     

Genetic control of responses to bacterial lipopolysaccharides in mice. II. A gene that influences a membrane component involved in the activation of bone marrow-derived lymphocytes by lipipolysaccharides.

C3H/HeJ mice contain a defect in a single autosomal locus which is not linked to the H-2 histocompatibility or the heavy chain allotype loci that restrict immune, mitogenic, and polyclonal responses to bacterial lipopolysaccharides (LPS). Adult thymectomized C3H/HeJ mice that have been irradiated and reconstituted with C3HeB/FeJ bone marrow cells respond well to LPS. Cell-mixing experiments using C3H/HEJ-C3HeB/FeJ spleen cultures show that the failure of C3H/HeJ spleen cells to support responses to LPS is not due to nonspecific or LPS-induced suppressive events, or the lack of accessory cell types. C3H/HeJ and C3HeB/FeJ spleen cells bind LPS and respond to other B cell mitogens equally well. We suggest that the B lymphocytes of C3H/HeJ mice have a defect in a membrane component that is activated via interaction with LPS, and initiates the intracellular events that lead to cell proliferation.     

In vitro stimulation of C3H/HeJ spleen cells and macrophages by a lipid A precursor molecule derived from Salmonella typhimurium

C3H/HeJ mice possess a genetic lesion that renders them significantly less responsive to the biologic effects of protein-free lipopolysaccharide (LPS) preparations, and more specifically, to the lipid A region of the LPS molecule. The in vivo manifestations of this mutation are also reflected in vitro in that cells derived from this mouse strain fail to respond to LPS when compared with cells derived from fully endotoxin-responsive mouse strains. The precise nature of this gene defect has not yet been established. In this study, we have examined in vitro the biologic activities of a structurally less complex "lipid A precursor" molecule, produced by a conditionally lethal, temperature-sensitive mutant of Salmonella typhimurium. In contrast to the intact LPS or wild-type lipid A extracted from the parental strain of Salmonella typhimurium, the lipid A precursor induced a highly significant, polymyxin B-inhibitable mitogenic response in splenic cultures derived from LPS-hyporesponsive C3H/HeJ and C57BL/10ScN (nu/nu) mice. In addition, the lipid A precursor was found to stimulate cultures of C3H/HeJ macrophages to produce significant levels of both interleukin 1 (IL 1, previously referred to as "lymphocyte activating factor" or "LAF") and prostaglandins of the E series (PGE). These findings suggest the possibility that the defect in endotoxin responsiveness exhibited by C3H/HeJ mice may be related to a defect in the processing of wild-type lipid A or LPS to a suitably stimulatory form that is structurally related to the lipid A precursor molecule.     

Activation of C3H/HeJ macrophage tumoricidal activity and cytokine release by R-chemotype lipopolysaccharide preparations. Differential effects of IFN-gamma

We have investigated the relative immunostimulatory activities of S-chemotype LPS and R-chemotype LPS preparations on C3H/HeJ peritoneal macrophages in vitro. As assessed by either secretion of TNF-alpha or IL-1, some of the R-chemotype LPS manifest significant activity on these normally LPS-unresponsive cells. The expression of IL-1 activity by R-LPS-stimulated C3H/HeJ macrophages was unaffected by IFN-gamma; however, this cytokine significantly enhanced TNF-alpha production by the same cells. The R-chemotype LPS preparations alone were not able to activate C3H/HeJ macrophages to become tumoricidal but activity could readily be demonstrated in the presence of IFN-gamma. Of potential importance is the observation that the profile of relative activity of the various R-chemotype LPS preparations for macrophage activation does not parallel that previously obtained by us for the C3H/HeJ B-lymphocyte activation.     

Refractoriness to migration inhibitory factor of macrophages of LPS nonresponder mouse strains.

The responsiveness to macrophage migration inhibitory factor (MIF) of peritoneal exudate cells (PEC) from the LPS unresponsive C3H/HeJ and C57BL/10ScCR mice was assessed by the indirect agarose microdroplet macrophage migration inhibition assay. No migration inhibition with PEC from C3H/HeJ nor C57BL/10ScCR mice was detected, whereas PEC from both C3H/HeN and C57BL/10Sn mice were significantly inhibited by even a 1/32 dilution of MIF-containing supernatants. Responsiveness to MIF of C3H/HeJ PEC could, however, be induced. In vivo inoculations of Mycobacterium bovis, strain BCG, 7 days before in vitro assay rendered C3H/HeJ PEC responsive to MIF. The lack of responsiveness to MIF by C3H/HeJ PEC appeared related to some form of suppression, since a mixture of PEC from C3H/HeN mice with 10 to 15% PEC from C3H/HeJ mice resulted in undetectable migration inhibition at any MIF dilution. In contrast to the usual lack of responsiveness of their macrophage to MIF, C3H/HeJ mice were able to produce MIK in response to PPD as well as their counterpart C3H/HeN mice after BCG sensitization. These results demonstrate that macrophages from C3H/HeJ and C57BL/10ScCR mice are unable to be inhibited in their in vitro migration of MIF (possibly being directly or indirectly influenced by a suppressor cell), whereas lymphoid cells from at least one of these strains, the C3H/HeJ mice, can produce MIF in response to antigenic stimulation.     

The effects of LPS on the cellular composition of the splenic white pulp in responder C3H/He and non-responder C3H/HeJ mice

The aim of the present study was to compare the effects of LPS on the cellular composition of the splenic white pulp in responder C3H/He and non-responder C3H/HeJ mice. The present results show that an intravenous injection of LPS in C3H/He mice results in a number of prominent changes in the histology of the spleen, but none of these histological changes could be demonstrated in the unresponsive C3H/HeJ mice. However, the present study shows that LPS administration resulted in the disappearance of previously trapped immune complexes from the follicles in both responder C3H/He and non-responder C3H/HeJ mice. The significance of this phenomenon is discussed. The localization of intravenously injected LPS in both mouse strains was compared using an immunoperoxidase technique. Most of the injected LPS was taken up by marginal zone macrophages at 2 h after administration. No major differences could be detected in the localization pattern of LPS between C3H/He and C3H/HeJ mice. The present results support the suggestion that the genetically based unresponsiveness of C3H/HeJ mice could be due to an intracellular defect in their response to LPS.     

Characterization of a congenitally LPS-resistant, athymic mouse strain.

C57BL/10ScN (nu/nu) mice have B cells and macrophages unresponsive to a phenol-water extracted preparation of Escherichia coli K 235 LPS. This unresponsiveness was demonstrated in vitro by the inability of spleen cells to incorporate 3H-thymidine after a 48 hr incubation with LPS (Ph) and by the inability of LPS (Ph) to inhibit macrophage phagocytosis of 51 Cr-labeled, opsonized sheep erythrocytes. Furthermore, macrophage cultures stimulated with LPS (Ph) produced low levels of LAF and PGE2 when compared with macrophages from the LPS-sensitive C3H/HeN and C3H/HeN (nu/nu) strains. Therefore, the C57BL/10ScN (nu/nu) strain is similar in its LPS unresponsiveness to the well-characterized C3H/HeJ and C57BL/10ScCR strains. The combination of endotoxin unresponsiveness and the athymic nature of this mouse strain may provide a powerful new tool for studying the cellular events mediating endotoxicity.