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.     

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.     

Influence of RU 41.740, a glycoprotein extract from Klebsiella pneumoniae, on the murine immune system. I. T-independent polyclonal B cell activation

A glycoprotein extract from Klebsiella pneumoniae, RU 41.740, has been shown clinically to reduce infectious episodes in patients prone to frequent infections, and experimentally to reduce mortality in animals infected with various bacteria or viruses. The method of action of RU 41.740 in conferring protection from infection is as yet unknown, but in experimental animals, RU 41.740 appears to influence B and T cells as well as macrophages. We report here that RU 41.740 is a strong polyclonal B cell activator and that it activates B cells in a T-independent manner. RU 41.740 also activates spleen cells from the LPS-nonresponder mouse strains, C3H/HeJ and C57BL/10ScCr, which indicates that the polyclonal B cell activating ability of RU 41.740 is not due to contamination by 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.     

Association of Lps gene with natural resistance of mouse macrophages against Legionella pneumophila.

Peritoneal macrophages obtained from lipopolysaccharide (LPS)-low responder C3H/HeJ mice (J) permitted the intracellular growth of the bacterium in macrophages of (J x N) F1 progeny was between the parent strains, showing that the traits were co-dominantly expressed. Correlation between intracellular bacterial growth in macrophages and LPS response of spleen cells was examined. Negative correlation was found between the two factors in F2, (J x F1) backcross and (N x F1) backcross progeny. This result implies that Lps gene controls the innate resistance of murine macrophages against the bacteria. Although macrophages of A/J strain also permit intracellular growth of L. pneumophila, gene complementation analysis of A/J and C3H/HeJ mice made clear that the gene control in C3H/HeJ differs from that of A/J strain. Macrophages of C57BL/10ScN, which is LPS-low responder line obtained from C57BL/10, were also defective in controlling the bacterial growth when compared to C57BL/10 mice. We suggest that the Lps gene also controls the natural resistance of murine macrophages against L. pneumophila.     

Variation among mouse strains in responsiveness to migration inhibitory factor.

Mineral oil-induced peritoneal exudate cells (PEC) from 10 different inbred mouse strains were tested for their responses to macrophage migration inhibitory factor (MIF). PEC from 5 out of 10 mouse strains responded to MIF, PEC from BALB/c mice showed an intermediate responsiveness, and PEC from A/J, C3H/HeJ, CBA/N, and C57BL/10ScCR mice were refractory to MIF. MIF responsiveness was not linked to the H-2 complex. However, a possible link between responsiveness to LPS and MIF was suggested, since the mouse strains not responding to MIF were previously reported to be deficient for responses to LPS.     

Relationship between immune system and gram-negative bacteria. IV. T lymphocytes from Lpsd mice possess binding site(s) for Rb Salmonella

We have previously shown that Salmonella minnesota R345 (Rb) spontaneously binds to 50 to 55% of human peripheral blood mononuclear cells (PBMC). In the present study, we have compared Rb cytoadherence to lymphoid cells from various tissues of lipopolysaccharide (LPS) hyporesponsive (Lpsd) and LPS responsive (Lpsn) mouse strains. A higher number of spleen cells from Lpsd mice (C3H/HeJ and C57BL/10ScN) bound Rb bacteria (22 to 30%) than cells from Lpsn mice (4 to 9%). Rb bound mainly to T cells, and cytoadherence occurred in both Lyt-1+ and Lyt-2+ T cell subsets. By contrast, purified splenic B cells from Lpsd and Lpsn mice gave less than 4% Rb cytoadherence. In both mouse strains, cytoadherence was mediated by the homologous LPS structure, because purified Rb-LPS blocked Rb Salmonella binding to T cells. On the other hand, smooth Salmonella typhimurium LT-2 LPS (S-LPS) and Salmonella R595 (Re) LPS (Re-LPS), which contain mainly lipid A, were without effect on Rb binding. Increased Rb binding was seen with T cells from Peyer's patches (PP), mesenteric lymph nodes (MLN), and peripheral blood than from spleen of C3H/HeN (Lpsn) mice; however, greater cytoadherence was always seen with T cells of these tissues from C3H/HeJ mice. Interestingly, treatment of whole spleen or purified T cells from C3H/HeN mice with neuraminidase enhanced cytoadherence to levels seen with C3H/HeJ cells. The observed Rb binding to PP, MLN, and PBMC cells in both mouse strains suggests that gut microbial environment may play an important role in Rb cytoadherence. This is also supported by the evidence that when spleen cells of germfree and conventional mice were tested for Rb binding, higher cytoadherence was observed in conventional mice only. Taken together, these results indicate that T cells of Lpsd mice express binding site(s) for Salmonella, whereas Lpsn mice have T cells with these structure(s) in a cryptic configuration.     

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.     

Genetic basis of murine antibacterial defense to streptococcal lung infection

To evaluate the effect of genetic background on antibacterial defense to streptococcal infection, eight genetically diverse strains of mice (A/J, DBA/2J, CAST/Ei, FVB/NJ, BALB/cJ, C57BL/6J, 129/SvImJ, and C3H/HeJ) and tlr2-deficient mice (C57BL/6^tlr2−/−) were infected with three doses of Streptococcus zooepidemicus (500, 5,000, or 50,000 colony-forming units) by alveolar challenge. There was a range of susceptibility between the strains at each dose and time point (6, 24, and 96 h). At the lowest dose, the 129/SvImJ and C3H/HeJ strains had significantly higher bacterial counts at all time points after infection, when compared to A/J, DBA/2J, CAST/Ei, FVB/NJ, which were resistant to infection at the low dose of innoculum. At the medium dose, 129/SvImJ and C3H/HeJ had higher bacterial counts, while A/J, DBA/2J, and BALB/cJ showed reduced streptococcal growth. After the highest dose of Streptococcus, there were minimal differences between strains, suggesting the protective impact of modifier genes can be overcome. TLR2-deficient animals contained increased bacterial load with reduced cytokines after 96 h when compared to C57BL/6J controls suggesting a role of innate immunity in late antibacterial defense. Overall, we identify vulnerable (129/SvlmJ and C3H/HeJ) and resistant (A/J, FVB, and DBA) mouse strains to streptococcal lung infection, which demonstrate divergent genetic expression profiles. These results demonstrate that innate differences in pulmonary host defense to S. zooepidemicus are dependent on host genetic factors.     

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.     

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.     

Susceptibility to pulmonary hypertension in inbred strains of mice exposed to cigarette smoke.

Cor pulmonale is a significant cause of morbidity and mortality in patients with emphysema, but it is not known whether alveolar destruction is directly involved in the disease pathogenesis. The purpose of this study was to examine the relationship between susceptibility to smoking-induced cor pulmonale and alveolar destruction in eight inbred strains of mice: 129XI/SvJ, A/J, A/HeJ, BALB/cJ, C3H/HeJ, C57BL/6J, DBA/2J, and SWR/J. The mice were exposed to filtered air or mainstream cigarette smoke at a concentration of 250 mg/m(3) for 5.5 h/day, 5 days/wk for 5 mo, housed for 4 more months, and killed. The ratio of the weight of the right ventricle/left ventricle plus septum [RV/(LV + S)] was used to assess right ventricular hypertrophy. Alveolar mean linear intercept was used to quantify severity of alveolar destruction. Morphometric determination of blood vessel muscularization was done on sections from four mouse strains. Smoke exposure resulted in significant increases in RV/(LV + S) in the A/J and A/HeJ strains compared with air-exposed controls. The magnitude of the smoking-induced increase in RV/(LV + S) decreased as a function of the genetic distance of the other strains from the A/J and A/HeJ strains. Pulmonary vascular muscularization was significantly increased in smoke-exposed A/J and BALB/cJ mice but not in C3H/HeJ and C57BL/6 mice. Also, mouse strain susceptibility to smoking-induced pulmonary vascular muscularization did not correlate with changes in mean linear intercept. The data from this study suggest that alveolar destruction by itself is not sufficient to cause smoking-induced cor pulmonale in inbred mice.     

The physical separation of Lps and Ifa loci in BXH recombinant inbred mice

Several reports in the literature suggest that many of the phenotypic defects of LPS-hyporesponsive C3H/HeJ mice may be attributed to decreased IFN production by their macrophages. The physical proximity on chromosome 4 of the gene which encodes sensitivity to LPS (Lps) and the structural gene cluster which encodes IFN-alpha (Ifa), suggests the possibility that the Lps gene, whose product is unknown, may actually be a part of the Ifa gene cluster. The C57BL/6J and C3H/HeJ mouse strains carry distinct alleles at both the LPs and the Ifa loci. In this study, we have analyzed these parental strains, as well as 12 recombinant inbred strains derived from these parental strains (e.g., BXH strains), for inheritance of these distinct alleles. The results show the segregation of these two loci: in 5 of 12 BXH RI strains, the IFN-alpha restriction fragment length polymorphism characteristic of one parental strain was discordant with the predicted LPS response phenotype. Therefore, we conclude that the Lps and the Ifa genes are physically distinct despite the apparent cause and effect relationship which is observed phenotypically.     

Complement Split Product C5a Mediates the Lipopolysaccharide-Induced Mobilization of Cfu-S and Haemopoietic Progenitor Cells, But Not the Mobilization Induced By Proteolytic Enzymes

Abstract. Intravenous (i.v.) injection of mice with lipopolysaccharide (LPS), and the proteolytic enzymes trypsin and proteinase, mobilizes pluripotent haemopoietic stem cells (CFU-s) as well as granulocyte-macrophage progenitor cells (GM-CFU) and the early progenitors of the erythroid lineage (E-BFU) from the haemopoietic tissues into the peripheral blood. We investigated the involvement of the complement (C) system in this process. It appeared that the early mobilization induced by LPS and other activators of the alternative complement pathway, such as Listeria monocytogenes (Lm) and zymosan, but not that induced by the proteolytic enzymes, was absent in C5-deficient mice. the mobilization by C activators in these mice could be restored by injection of C5-sufficient serum, suggesting a critical role for C5.
The manner in which C5 was involved in the C activation-mediated stem cell mobilization was studied using a serum transfer system. C5-sufficient serum, activated in vitro by incubation with Lm and subsequently liberated from the bacteria, caused mobilization in both C5-sufficient and C5-deficient mice. C5-deficient serum was not able to do so. the resistance of the mobilizing principle to heat treatment (56°C, 30 min) strongly suggests that it is identical with the C5 split product C5a, or an in vivo derivative of C5a. This conclusion was reinforced by the observation that a single injection of purified rat C5a into C5-deficient mice also induced mobilization of CFU-s.     

Susceptibility of inbred mice to Leishmania tropica infection: correlation of susceptibility with in vitro defective macrophage microbicidal activities

Eleven mouse strains were inoculated in footpads with amastigotes of Leishmania tropica and observed for 12 weeks. Liver and spleen impression smears from infected mice were examined for the presence of intracellular parasites. Four strains (BALB/cJ, C57L/J, NZW/N, and P/J) failed to heal the subcutaneous lesion and showed evidence of systemic infection; the remaining seven strains (A/J, C3H/HeJ, C3H/HeN, C3HeB/FeJ, C57BL/6J, C57BL/10J, and C57BL/10ScN) were each resistant to infection and resolved their lesions by Week 10. Macrophages from the four susceptible strains could not be activated to kill L. tropica amastigotes by treatment with soluble lymphocyte products in vitro. In contrast, macrophages from all seven resistant strains responded to lymphokine treatment and eliminated 80-90% of intracellular parasites. These results suggest that in vitro macrophage microbicidal activities predict the course of systemic leishmanial disease.     

Generation of lipopolysaccharide-induced interferon in spleen cell cultures

Incubation of murine spleen-cell cultures with lipopolysaccharide (LPS) induces interferon (IF) production. Maximal IF levels are obtained after incubation with 100 g/ml for 10 h. Two inbred mouse strains differing in their ability to generate LPS-induced IF in spleen-cell cultures were used: C3H/eB, which generates high levels of IF (about 60 units/ml), and C3H/HeJ, which fails to generate detectable quantities of IF. In a genetic analysis these strains were hybridized and IF production was determined in spleen-cell cultures from F₁ and F₂ generations, and from backcrosses of F₁ hybrids to parent strains. The results indicate that, in parent strains, a single dominant autosomal gene is responsible for differences in IF production in spleen cultures. LPS-induced IF in spleen-cell cultures resists pH 2 for as long as 48 h, but is labile to heating at 56° C for 30 min. Both macrophages and lymphocytes must be present in cultures for generation of LPS-induced IF. By using mixed cultures of macrophages and lymphocytes from C3H/eB and C3H/HeJ mice, it was shown that macrophages have to interact directly with LPS to enable IF production in the cultures.     

Mitogenic,immunoadjuvancy, and genetic studies on fatty acyl maltose

Summary Three synthetic glycolipids, maltose tetrapalmitate (MTP), maltose hexastearate (MHS), and maltose hexalinoleate (MHL) prepared as nontoxic lipid A analogs, and Escherichia coli lipopolysaccharide (LPS) were assayed for their mitogenic activity using spleen lymphocytes in nine inbred mouse strains and three F1 hybrids. The MTP and LPS were also assayed for their ability to enhance plaque-forming cell (PFC) responses using sheep red blood cells as the antigen in th same inbred mouse strains and F1 hybrids, The mitogenic activity of synthetic glycolipids was several fold lower than that of LPS and MHL was inferior to MTP and MHS. DBA/2J was the most responsive strain for MTP and DBA/1J and C3H/HeJ the least. The mitogenic activity of MTP was generally in agreement with the PFC response stimulation by it. Lowdose cyclophosphamide treatment of mice synergized MTP for PFC response augmentation. Genetic studies on MTP mitogenicity revealed that 90% of responder DBA/2J X nonresponder C3H/HeJ F1 hybrids had intermediate mitogenic activity. Among F2, 73% had intermediate-high activity and 27% were nonmitogenic. Among F1 X C3H/HeJ backcrosses 11% had high, 56% intermediate, and 33% had no mitogenic activity, whereas, for the F1 X DBA/2J backcross, 14% had high, 36% intermediate, and 50% low or negligible activity. The data favored a single gene for MTP activation of immune cells.This work was supported, in part, by a grant from the National Cancer Institute of Canada, and by grant from the Cancer Research Society Inc.     

Further studies on mobilization of CFUs.

Mobilization of CFUs from haemopoietic tissues into circulation was studied after injection of different bacterial lipopolysaccharides (LPS), zymosan, phytohaemagglutinin (PHA), concanavalin A (Con A), trypsin and di-isopropyl-fluorophosphate-inhibited trypsin. All bacterial LPS used gave an increase of CFUs in the peripheral blood at 1 h after i.v. injection. Some variation in activity could not be excluded. As with Salmonella typhosa LPS, zymosan gave an increase in circulating CFUs during the first few hr and a second peak a few days later. After injection of zymosan as well as S. typhosa LPS the second peak in the blood was accompanied by a large increase in CFUs numbers in the spleen. PHA gave an immediate mobilization of CFUs, but the mobilization after injection of Con A during the first few hr occurred more slowly. After injection of S. typhosa LPS, zymosan and PHA the blood C3 level was found to be depressed considerably. This might indicate that the complement system is involved in the early mobilization of CFUs. Dexamethasone, a synthetic hormone which has been reported to give sequestration of several cell types in the bone marrow, did not inhibit the early and late mobilization of CFUs which normally occurs after injection of S. typhosa LPS.     

Activation of murine B lymphocytes by suramin

Suramin stimulated DNA synthesis in spleen cell cultures of all inbred strains of mice tested, including, for example, CBA, DBA/2, C57BL/6, and the lipopolysaccharide (LPS)-nonresponsive strain C3H/HeJ. The cells responding to the drugs were removed by passage through nylon wool columns, but they were not eliminated by in vivo treatment of the mice with anti-Thy 1.2 antibody. Spleen cells of homozygous nude mice (C57BL/6 or BALB/c background) were as reactive as those of their heterozygous littermates. Collectively the data show that suramin is a B-cell mitogen in the mouse.     

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.