Suppression of the immune response in C3H/HeJ mice by protein-free lipopolysaccharides

Reduced inflammatory factor expression facilitates recovery after sciatic nerve injury in TLR4 mutant mice

Toll-like receptors (TLRs) are extremely significant pattern recognition receptors. When nerve injury occurs, a variety of inflammatory factors are generated, leading to an exceedingly complex micro-environment. TLRs recognize damage-associated molecular patterns. To investigate the correlation between TLR4 and recovery after sciatic nerve injury, the model of sciatic nerve injury was conducted using TLR4-mutated mice (C3H/HeJ) and wild mice (C3H/HeN). Our goal was to identify short-stage and long-stage changes after sciatic nerve injury, mainly by checking the expression changes of inflammation factors in the short-stage and the differences in the recovery of the injured sciatic nerve in the long-stage. The results show that the increase of changes in the HeN group of IL-1β, IL-6, TNF-α and MCP-1 are more obvious than in the HeJ group, with caspase1 expression higher and Nlrp3 expression lower in the former group. Further results reveal intense inflammation occurred in the HeN group showing more neutrophils and macrophages. Nlrp3 and caspase1 showed little difference by Immunohistochemistry, with Nlrp6 expression differing between the HeJ group and the HeN group. The results led us to conclude that better recovery of the injured sciatic nerve occurred in the HeJ group because the expression of GAP-43 and p75NTR was higher and had a better SFI figure. TLR4 mutation can decrease the expression of inflammatory factors and enhance the speed of recovery after sciatic nerve injury. The changes in the expression of Nlrp6, which are related to the TLR4 mutation, may influence recovery of the injured sciatic nerve. Further studies will be conducted to confirm these results.

Resistance to experimental autoimmune thyroiditis is correlated with the duration of raised thyroglobulin levels

We have used the mouse model of experimental autoimmune thyroiditis (EAT) to examine the hypothesis that the strengthening of self-tolerance to thyroglobulin by exogenous mouse thyroglobulin (MTg) or stimulation of endogenous MTg secretion by thyroid-stimulating hormone (TSH) is correlated with the length of time MTg rises above the normal range. Bacterial lipopolysaccharide (LPS) treatment increases the initial half-life of MTg from about 3 hr to about 5 hr, probably interfering with its clearance by the mononuclear phagocytic (reticuloendothelial) system. By pretreating mice with LPS, a subtolerogenic MTg dose is rendered tolerogenic. Similarly the effect of TSH infusion by osmotic minipumps, which stimulates MTg secretion and also strengthens tolerance to MTg, can be enhanced by injecting LPS shortly after pump implantation. The resulting increase in MTg level (due to delayed clearance of MTg) is greater than that from TSH alone and suppresses further the animals' susceptibility to disease induction by MTg and adjuvant. Moreover, resistance following pretreatment with LPS and subtolerogenic MTg is mediated by CD4+ suppressor T cells, as shown recently for the suppression in mice given high doses of tolerogenic MTg. These experiments are in full agreement with the hypothesis and confirm that small increases in circulating MTg concentrations, which could occur physiologically, can be effective in protecting against EAT induction.

Expression of immunoreactive growth hormone in leukocytes in vivo

In the present study, we investigated the production of growth hormone (GH)-related RNA and protein in vivo by rat leukocytes after intraperitoneal treatment with different inducing agents including bacterial lipopolysaccharide (LPS) and Freund's complete adjuvant (FCA). The data showed that in rats after exposure to LPS or FCA leukocytes obtained from the spleen, thymus, and peritoneum all showed a dose-dependent increase in GH-related RNA content. The peak production of GH-related RNA was observed 48 h after treatment in the spleen and thymus and 96 h after treatment in the peritoneum. We also evaluated the ability of LPS-sensitive (C3HeB/FeJ) and resistant (C3H/HeJ) inbred mice treated with LPS to produce GH-related RNA. The LPS-sensitive mice presented with a typical pathophysiologic response pattern and higher levels of GH-related RNA in the spleen and thymus than the LPS-resistant mice. An increase in the production of immunoreactive GH (irGH) was also observed by direct immunofluorescence with specific antibodies to rat GH. We validated that the GH-related RNA produced in vivo by leukocytes was similar in structure to pituitary GH RNA using reverse transcription and the polymerase chain reaction (PCR). A sample of the PCR reaction, analyzed by gel electrophoresis, showed a single major DNA band corresponding in length (600 base pairs) to the distance between the 5'-ends of the two GH-specific primers that was specifically detected with a GH-specific probe after Southern transfer. In other studies with normal nontreated animals, the GH RNA levels are higher in the evening hours and early on in the first month of life. Taken together, our data are the first demonstration that GH RNA and immunoreactive protein can be detected in leukocytes in vivo both in normal and stimulated animals and support the idea that GH may be active in an immune response.

Side effects of antibiotics on immune response parameters and their possible implications in antimicrobial chemotherapy

Antibiotics may influence immune response by quite different ways. By screening the multitude of publications on this subject, the aim of this overview was to arrive at a basic generalizing statement on the relationship between chemical structure or mode of action of antibiotics and the effect on immune response and to get an indication on whether certain in vitro and/or ex vivo parameters could represent comparable effects under clinical conditions. - The influence of antibiotics on immune response may arise by direct effects on immunocompetent cells, i.e. in the absence of microorganisms, or indirectly by changes in structure or metabolic products of germs induced by subminimal inhibitory concentrations (subMIC's). In the former case, stimulatory and inhibitory effects have been observed on phagocytosis and intracellular killing activity, on antibody production including IgE, on different parameters of cellular immunity (e.g. foodpad swelling reaction, MIF-production, mitogen/antigen induced lymphocyte proliferation and delayed type hypersensitivity skin reaction), on mediator production as interleukins or prostaglandins and the expression of corresponding receptors on immunocompetent cells as well as on the course of experimental infections with primary resistant microorganisms. - Indirect effects are related to the influence of subMIC's of antibiotics on the morphology and structure of microorganisms, on their antigenicity/immunogenicity or on their serosensitivity and enzyme and toxin production. - This overview shows that - according to the actual knowledge - antibiotics may exhibit immunological side effects which, however, can not strictly be attributed to certain chemical structures or to a certain mode of action. - It has to be considered that a literary study comparing the results of different authors is rendered difficult by the often nonhomogeneity of experimental procedures and the fact that little is known yet about immunological side effects of antibiotics in man, i.e. under clinical conditions.

Animal studies of toxic shock syndrome

Toxic shock syndrome (TSS) was first described in 1978 and since that year over 2990 cases have been reported to the Communicable Disease Center. The estimated case-fatality rate is 5.6%. The disease is characterized by fever, hypotension, rash, desquamation, and involvement of at least three other organ systems. Approximately 85% of the cases are menstrually related and tampon use has been identified as a risk factor. The remaining 15% of the cases occur in both sexes and are not specifically related to age or geographic location. In all cases where sought there is evidence for infection by Staphylococcus aureus. Nearly all S. aureus isolates are phage type 52/29 and elaborate a unique exotoxin (toxic shock toxin). This review explores both the successful and unsuccessful attempts to induce toxic shock or a TSS-like syndrome in animals other than man. The review identifies the baboon as an animal model of TSS and discusses the clinical and pathologic sequellae, in this species, after exposure to purified toxic shock toxin.

Mitogenic activities of synthetic lipid A analogs and suppression of mitogenicity of lipid A

The effect of synthetic lipid A analogs on murine spleen cells was studied. The preparations represented D-glucosamine and D-glucosaminyl-beta 1,6-D-glucosamine disaccharide derivatives substituted in different combinations by ester- and amide-bound fatty acids and by phosphate groups. Significant mitogenic activity was demonstrated with a number of synthetic disaccharide preparations; however, their potency was lower than that of lipid A. The synthetic preparations were not mitogenic for spleen cells from C3H/HeJ mice. Furthermore, the mitogenicity of the synthetic preparations was abolished after binding with polymyxin B. The results indicate that for expression of mitogenicity, a phosphate group at position 1 of the reducing glucosamine and amide-bound acyloxyacyl residues are important factors. Some of the synthetic preparations containing the diglucosamine backbone and expressing relatively low mitogenicity suppressed B-cell mitogenicity of lipid A. Although these preparations were lytic for erythrocytes, they did not affect the viability of the splenic lymphocytes. Suppression was seen when the synthetic preparations were added simultaneously with or after the lipid A mitogen, but optimal suppression was expressed when the preparations were added to the system 3 h before lipid A. Washing of the cells before the addition of lipid A did not affect the results. The suppression was not due to the induction of suppressor cells by the synthetic preparations. The disaccharide preparations did not inhibit T-cell mitogenicity of concanavalin A. In contrast to the disaccharide preparations, the monosaccharide preparations suppressed mitogenicity of both lipid A and concanavalin A, probably because of their direct toxicity for lymphocytes.

Lipopolysaccharide-induced activation of suppressor cells: reversal by an agent which alters cyclic nucleotide metabolism

The effects of bacterial lipopolysaccharides (LPS) on the suppressor activity of mouse spleen cells were examined. Pretreatment with LPS was shown to induce suppressor activity in vivo and in vitro. Concurrent treatment of spleen cells with LPS and imidazole, an agent which increases the activity of cyclic nucleotide phosphodiesterases and hastens the degradation of cyclic AMP, reversed the suppressor-inducing effects of LPS. In vitro treatment of spleen cells with aminophylline, an agent which inhibits phosphodiesterase activity, had no effect on suppressor activity. The reversal of LPS-induced suppressor activity by imidazole was time-dependent and addition of this agent 20 hr after LPS treatment did not reverse suppression. These data are consistent with the hypothesis that LPS-induced suppressor activity may be mediated via cyclic AMP-dependent pathways.

Endotoxin depression of hepatic mixed function oxidase system in C3H/HeJ and C3H/HeN mice

The effect of endotoxin to depress the hepatic drug-metabolizing enzyme activity has been studied in the C3H/HeJ and C3H/HeN strains of mice. The C3H/HeJ mouse strain is generally considered to be unresponsive to the biological effects of endotoxin. However, injection of these mice with 0.5 mg/kg body weight of E.coli endotoxin (Westphal extracted) produced a decrease in the rate of N-demethylation of ethylmorphine and in the levels of cytochrome P-450 and cytochrome b5 comparable to that observed in the endotoxin-sensitive C3H/HeJ mouse strain. Although the mechanism of endotoxin action to decrease hepatic microsomal drug-metabolizing activity is presently unknown, the results suggest that: 1) the C3H/HeJ mouse stain is responsive to this endotoxin effect, and 2)that cellular constituents other than B-cells or macrophages are probably involved in eliciting the response, since these cells of the C3H/HeJ mouse are unresponsive to endotoxin.

New phenotypic marker for lipopolysaccharide responsiveness

Lipopolysaccharide-enhanced secretion of non-immunoglobulin proteins by bone marrow cells derived from responder, nonresponder, and low-responder mouse strains did not precisely correlate with the lipopolysaccharide responsiveness assessment based on the mitogenic reactivity of splenocytes. These findings suggest that enhancement of secretion of non-immunoglobulin protein may be useful for further characterization of lipopolysaccharide responsiveness.

Influence of lipopolysaccharide on graft versus host reactivity of lipopolysaccharide-unresponsive C3H/HeJ mice

It was initially reported that lipopolysaccharide (LPS)-unresponsive C3H/HeJ mice are refractory to LPS at the B-lymphocyte level, but more recently it has been shown that other cells are similarly unaffected. The current study was undertaken to study an in vivo LPS-modulated disease process involving macrophage-T cell interactions. Adult CBA/J and C3H/HeJ mice were used as spleen donors, and graft versus host reactions were induced in BALB/c neonates. Prior LPS treatment of CBA/J adults decreased the ability of their spleen cells to cause fatal graft versus host disease in BALB/c neonates, whereas no difference was found between injection of spleen cells from normal or LPS-treated C3H/HeJ mice. Similar results were obtained with these cell types when the mouse spleen mixed leukocyte culture system was used. In a carbon clearance assay for stimulation of the reticuloendothelial system with LPS, it was found that the rate of phagocytosis was significantly increased in BALB/c and CBA/J mice 72 h after inoculation of LPS. No stimulation was seen in rate of carbon uptake in the C3H/HeJ animals after treatment with phenol-extracted LPS or with butanol-extracted LPS. An LPS-induced protective serum factor was produced only in the LPS-responsive CBA/J mice and was specific for the syngeneic cells.

Modulation of the immune response to sheep erythrocytes by lipid-free glycerol teichoic acid

The 4-day response of C3H/HeJ mice to sheep erythrocytes was suppressed by a lipid-free teichoic acid with an average molecular weight of 2,900 when it was administered by the intraperitoneal route. Enhancement was not observed at that time, and neither suppression nor enhancement could be demonstrated by the intravenous route. Either suppression or enhancement of background plaques could be induced, depending upon the timing. Dosage influenced the degree of suppression from 8 to 100 micrograms, whereas suppression of background plaques required only 1 microgram of lipid-free teichoic acid. The kinetics of the sheep erythrocyte response was altered by treatment of the mice with lipid-free teichoic acid, delaying the peak until day 5 and producing enhancement at that time. Although lipid-free teichoic acid was shown to be toxic for mouse splenocytes (50% lethal dose, ca. 200 micrograms) in vitro, no effect at the levels employed was observed in vivo. The data presented indicate that modulatory activity is influenced by route, timing, dosage, and apparently the number of antibody-secreting cells.

Analysis of the effects of lipopolysaccharide on macrophages: differential phagocytic responses of C3H/HeN and C3H/HeJ macrophages in vitro

The phenomenon of lipopolysaccharide (LPS)-induced in vitro macrophage cytotoxicity has been reported by a number of investigators but has often been difficult to reproduce and to quantitate. In this report, we have examined the effect of LPS on the ability of macrophages to ingest 51Cr-labeled, opsonized sheep erythrocytes as a method for examining the direct toxic effects of LPS on macrophages in vitro. By using this assy, we can clearly discriminate between LPS responder C3H/HeN macrophages and LPS nonresponder C3H/HeJ macrophages and demonstrate that LPS induces a profound inhibition of Fc-mediated phagocytosis in LPS responsive macrophages. Furthermore, low concentrations of LPS stimulate phagocytosis in macrophages derived for C3H/HeJ mice. The lipid A moiety of the LPS is responsible for the observed enhancement or inhibition of Fc-mediated phagocytosis. This assay was more sensitive than LPS-induced cytotoxicity, since inhibition of phagocytosis was detectable in cultures of LPS-sensitive macrophages even when cytotoxicity, assessed by trypan blue exclusion, was not. Thus, this assay represents an extremely sensitive method for analyzing the direct effects of LPS on macrophages.