The Postnatal Leptin Surge Supports Immune Cell Function in Rats.

BACKGROUND: Leptin plays an important role in the regulation of the immune response. There is a physiological surge of leptin in rodents during the neonatal period, which has mainly been studied in the context of brain development. However, little is known about the effects of this neonatal leptin surge on immunity. Therefore, we investigated whether blocking this leptin surge could affect several immune functions. METHODS: Male and female rats were injected subcutaneously with 5 mg/Kg/day of rat pegylated super leptin antagonist during the neonatal period (PND5-9). On the peripubertal period, relevant functions as well as cytokine release by spleen leukocytes were studied in these animals. RESULTS: The results showed that the animals significantly display an impaired anti-tumor NK activity and chemotactic and proliferation capacity of lymphocytes in response to mitogens. In addition, several cytokine concentrations, released under mitogen-stimulated conditions, were also altered. CONCLUSION: In conclusion, the neonatal leptin surge seems to be involved in the establishment of an adequate immune response and cytokine profile, which are crucial for the maintenance of a healthy life.

Collagen-induced arthritis in Dark Agouti rats as a model for study of immunological sexual dimorphisms in the human disease.

Collagen-induced arthritis (CIA) is a frequently used animal model of rheumatoid arthritis, human autoimmune disease that exhibits clear sex bias in incidence and clinical course. Female Dark Agouti rats immunized for CIA showed also greater incidence and higher arthritic score than their male counterparts. The study investigated sex differences in mechanisms controlling the primary immune responses in draining lymph nodes (dLNs), as a factor contributing to this dimorphism. The higher frequencies of CD4 + CD25 + Foxp3- cells, presumably activated effector T (Teff) cells, and IL-17+, IFN-γ + and IL-17 + IFN-γ + T cells were found in female compared with male rat dLNs. However, the frequency of CD4 + CD25 + Foxp3+ T regulatory cells (Treg) did not differ between sexes. Thus, CD4+ Teff cells/Treg ratio, and IL-17+ T cells/Treg and IFN-γ + T cells/Treg ratios were higher in female than in male rats, and among them was found lower frequency of PD-1+ cells. This suggested less efficient control of (auto)immune Th1/Th17 cell responses in female rat dLNs. On the contrary, the frequency of IL-4+ T cells was lower in female than in male rat dLNs. Consistently, the ratio of serum levels of collagen-specific IgG2a (IFN-γ-dependent, with an important pathogenic role in CIA) and IgG1 (IL-4-dependent) was shifted towards IgG2a in female compared with male rats. As a whole, the study suggests that sexual dimorphism in the control of T cell activation/polarization could contribute to sex bias in the susceptibility to CIA. Moreover, the study advises the use of animals of both sexes in the preclinical testing of new drugs for rheumatoid arthritis.

Selected Molecular Mechanisms Involved in the Parasite⁻Host System Hymenolepis diminuta⁻Rattus norvegicus.

The rat tapeworm Hymenolepis diminuta is a parasite of the small intestine of rodents (mainly mice and rats), and accidentally humans. It is classified as a non-invasive tapeworm due to the lack of hooks on the tapeworm's scolex, which could cause mechanical damage to host tissues. However, many studies have shown that metabolites secreted by H. diminuta interfere with the functioning of the host's gastrointestinal tract, causing an increase in salivary secretion, suppression of gastric acid secretion, and an increase in the trypsin activity in the duodenum chyme. Our work presents the biochemical and molecular mechanisms of a parasite-host interaction, including the influence on ion transport and host intestinal microflora, morphology and biochemical parameters of blood, secretion of antioxidant enzymes, expression of Toll-like receptors, mechanisms of immune response, as well as the expression and activity of cyclooxygenases. We emphasize the interrelations between the parasite and the host at the cellular level resulting from the direct impact of the parasite as well as host defense reactions that lead to changes in the host's tissues and organs.

Can serum cytokine profile discriminate irritant-induced and allergen-induced symptoms? A cross-sectional study in workers mostly exposed to laboratory animals.

BACKGROUND: In workers exposed mostly to laboratory animals (LA), symptoms may be due to irritants or allergens. Correct aetiological diagnosis is important for health surveillance. OBJECTIVES: This study aims to test whether work-related (WR) allergen-induced symptoms are associated with a cytokine profile distinct from that due to irritants. METHODS: In a cross-sectional study (n=114), WR respiratory and/or skin symptoms were assessed through a standardised clinical examination and sensitisation to rat and/or mouse allergen determined by serum immunoglobulin E. Serum cytokine concentrations were measured by multiplex assays. The predefined cytokine profiles 'sensitiser' (interleukin (IL)-4, IL-5, IL-13, eotaxin-1) and 'irritation' (IL-8, IL-17A, IL-17F, IL-22) were considered positive, when ≥3 concentrations exceeded the 95th percentile of the asymptomatic non-sensitised group. Results were examined by hierarchical clustering analyses (HCA) and multiple linear regression. Explorative analyses were carried out for nine additional cytokines. Exposure to allergens and endotoxin was assessed in a subpopulation. RESULTS: The prevalence of the profile 'irritation' was comparable in 28 symptomatic non-sensitised workers and 71 asymptomatic non-sensitised workers. HCA showed that nearly all symptomatic non-sensitised workers were gathered in two subclusters, characterised by high IL-17A levels, but different IL-8 levels. Multiple linear regression identified drug consumption and current complaints as confounders. Sensitised subjects were too few (n=14) for testing the profile 'sensitiser'. CONCLUSIONS: In this unselected population of LA workers, the profile 'irritation' did not prove to be a valuable health surveillance tool. Low power precluded assessment of the profile 'sensitiser'. The increased IL-17A concentration may originate from irritative constituents of organic dust.

Generation of Methicillin-Resistant Staphylococcus Aureus Biofilm Infection in an Immunosuppressed Rat Model.

BACKGROUND Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen responsible for many related infections, and immunosuppressed individuals are more susceptible. Its pathogenicity is associated with its virulence factors, resistance to antibiotics, and ability to form biofilm (BF). MRSA-BF infections in immunosuppressed patients pose great difficulties to clinical treatment. MATERIAL AND METHODS The study aimed to establish a model of MRSA-BF infection in rats with cyclophosphamide (CTX)-induced immunosuppression. For this, rats were administered CTX on days 1 and 4. White blood cells (WBC) were counted, then rats were inoculated with a clinical MRSA 17546 (t037) on day 5. Rats were sacrificed on days 6-10 and tissue samples were examined by scanning electron microscopy. RESULTS Using the dose of CTX: 150 (mg/kg) + 100 (mg/kg) is better than the other 2 programs as the survival rates of the immunocompromised rats were higher than in the other 2 immunosuppressive groups. The survival rate was not different between rats in the clean environment and in the SPF environment. However, the survival rate was affected by the sample acquisitions. Importantly, WBC counts started to decline on day 4, and then started to rise on day 9. Moreover, MRSA-BFs were formed earlier in immunosuppressed rats compared to the normal rats, as shown by scanning electron microscopy. CONCLUSIONS The study successfully established an immunosuppressed rat model of MRSA-BF infection, which provides methodological and data support for establishment of such animal models and is useful reference for related research. Our results may help further investigation of MRSA-BF infection.

The laboratory mouse and wild immunology.

The laboratory mouse, Mus musculus domesticus, has been the workhorse of the very successful laboratory study of mammalian immunology. These studies--discovering how the mammalian immune system can work--have allowed the development of the field of wild immunology that is seeking to understand how the immune responses of wild animals contributes to animals' fitness. Remarkably, there have hardly been any studies of the immunology of wild M. musculus domesticus (or of rats, another common laboratory model), but the general finding is that these wild animals are more immunologically responsive, compared with their laboratory domesticated comparators. This difference probably reflects the comparatively greater previous exposure to antigens of these wild-caught animals. There are now excellent prospects for laboratory mouse immunology to make major advances in the field of wild immunology.

Systemic injection of low-dose lipopolysaccharide fails to break down the blood-brain barrier or activate the TLR4-MyD88 pathway in neonatal rat brain.

We aimed to investigate whether peripheral low-dose lipopolysaccharide (LPS) induces the breakdown of the blood-brain barrier (BBB) and/or the activation of toll-like receptor 4 (TLR4) in the neonatal rat brain. Neonatal rats received intraperitoneal injections of low-dose LPS (0.3 mg/kg∙bw), and the BBB compromise was detected by Evans Blue extravasation and electron microscopy. Meanwhile, TLR4, adaptin myeloid differentiation factor 88 (MyD88), nuclear transcription factor kappa-B (NF-κB) p50 and tumor necrosis factor alpha (TNFα) in the neonatal rat brain were determined by quantitative real-time polymerase chain reaction (PCR) and Western Blot. Immunohistochemistry was used to determine the distribution and activation of microglia in the brain after LPS administration. It was demonstrated that Evans Blue extravasation was not observed in the brain parenchyma, and that tight junctions of cerebral endothelial cells remained intact after systemic injections of LPS in neonatal rats. Although intracerebroventricular injections of LPS activated microglia and up-regulated the expression of TLR4, MyD88, NF-κB p50 and TNFα in the neonatal rat brain, systemic LPS did not induce these responses. These findings indicate that while the neonatal rat brain responds to the direct intra-cerebral administration of LPS through robust TLR4 activation, systemic low-dose LPS does not induce the innate immune reaction or compromise the BBB in neonatal rats.

[Immunoallergic skin manifestations associated with new pets: three cases]. / Manifestations cutanées immuno-allergiques liées aux nouveaux animaux de compagnie : trois observations.

BACKGROUND: The number of household pets increased greatly during the twentieth century, with numbers of new pets (NP, i.e. any pets other than cats and dogs) rising especially sharply over the last decade. PATIENTS AND METHODS: We first of all report the case of a female patient with eczema lesions on areas skin coming into contact with a ferret, with removal of the animal resulting in wound healing, followed by two patients presenting atypical polymorphous erythema reactions induced by dermatophytes present in their pet rat. DISCUSSION: While the most common allergies are respiratory, allergic skin reactions, both immediate and delayed, may also result from contact with these new allergens. The animal itself or its environment may be the cause.

Frequent detection and characterization of hepatitis E virus variants in wild rats (Rattus rattus) in Indonesia.

One hundred sixteen rats (Rattus rattus) captured in Indonesia from 2011 to 2012 were investigated for the prevalence of hepatitis E virus (HEV)-specific antibodies and HEV RNA. Using an ELISA based on HEV genotype 4 with an ad hoc cutoff value of 0.500, 18.1 % of the rats tested positive for anti-HEV IgG. By nested RT-PCR, 14.7 % of the rats had rat HEV RNA, and none were positive for HEV genotype 1-4. A high HEV prevalence among rats was associated with lower sanitary conditions in areas with a high population density. Sixteen of the 17 HEV isolates obtained from infected rats showed >93.0 % nucleotide sequence identity within the 840-nucleotide ORF1-ORF2 sequence and were most closely related to a Vietnamese strain (85.9-87.9 % identity), while the remaining isolate differed from known rat HEV strains by 18.8-23.3 % and may belong to a novel lineage of rat HEV. These results suggest a wide distribution of rat HEV with divergent genomes.

Sensitization to rodents (mouse/rat) in an urban atopic population without occupational exposure living in Naples, Italy.

BACKGROUND: Until now no data on allergic sensitization to rodents allergens in Western Europe and Italy are available. The aim of this report was to investigate clinical significance and characteristics of IgE-mediated sensitization to mouse/rat (M/Rt) allergens in atopic subjects not occupationally exposed to these animals and living in urban area of Naples. METHODS: In 1765 consecutive outpatients, we selected all subjects with an immediate skin reaction to M/WRt dander clinical history including a carefijul evaluation ofthe modality of exposure, the results of skin-prick tests (SPTs) and specific IgE antibodies were recorded. RESULTS: Among 1185 SPT-positive patients, 22 were sensitized to M/Rt dander (respectively 1.60% and 0.59%). No patient was mono-sensitized Only three of 22 patients reported indoor conditions suggesting presence of rodents allergens at home. All patients exhibited low degree of SPT positivity and low levels of circulating IgE antibodies to M/WRt. Highfrequency of concomitant allergic sensitization to pet (and other animal) dander has been found. CONCLUSIONS: Our results suggest that role of allergic sensitization to rodents is negligible in atopic subjects without occupational exposure living in urban area of Naples. However, highly atopic individuals especially those already sensitized to common pet dander should be tested by SPTs/evaluation of serum specific IgE to rodents in the case they could begin an occupational exposure to M/Rt or keeping these animals as pets.

At last - rats lacking B cells.

The rat model is a widely used animal model in research, its popularity perhaps only surpassed by the mouse model. Rats are the preferred models for the study of transplantation and certain tumor and autoimmune diseases. In particular, the understanding of cardiovascular-related diseases and chronic inflammation has depended widely on the rat, from which models for both multiple sclerosis and rheumatoid arthritis have been derived. Until now, research in the rat has been hampered by a lack of precise gene-targeting technology in this model. This limitation, however, is rapidly changing; a recent example is the availability of B-cell-deficient rat strains obtained by the newly established zinc finger nucleases-targeting technology. As described in this issue of the European Journal of Immunology, genetic targeting of the rat, for example, using zinc finger nucleases-targeting technology, is likely to rapidly drive progress in the understanding of not only B-cell biology but also in the general understanding of rat disease models.

Autoimmunity and inflammation: murine models and translational studies.

Autoimmune and inflammatory diseases, including type 1 diabetes, multiple sclerosis, inflammatory bowel disease, and rheumatoid arthritis, constitute an important and growing public health burden. However, in many cases our understanding of disease biology is limited and available therapies vary greatly in their efficacy and safety. Animal models of autoimmune and inflammatory diseases have provided valuable tools to researchers investigating their aetiology, pathology, and novel therapeutic strategies. Although such models vary in the degree to which they reflect human autoimmune and inflammatory diseases and caution is required in the extrapolation of animal data to the clinical setting, therapeutic approaches first evaluated in established animal models, including collagen-induced arthritis, experimental autoimmune encephalomyelitis, and the nonobese diabetic mouse, have successfully progressed to clinical investigation and practice. Similarly, these models have proven useful in providing support for basic hypotheses regarding the underlying causes and pathology of autoimmune and inflammatory diseases. Here we review selected murine models of autoimmunity and inflammation and efforts to translate findings from these models into both basic insights into disease biology and novel therapeutic strategies.

AFLP genome scan in the black rat (Rattus rattus) from Madagascar: detecting genetic markers undergoing plague-mediated selection.

The black rat (Rattus rattus) is the main reservoir of plague (Yersinia pestis infection) in Madagascar's rural zones. Black rats are highly resistant to plague within the plague focus (central highland), whereas they are susceptible where the disease is absent (low altitude zone). To better understand plague wildlife circulation and host evolution in response to a highly virulent pathogen, we attempted to determine genetic markers associated with plague resistance in this species. To this purpose, we combined a population genomics approach and an association study, both performed on 249 AFLP markers, in Malagasy R. rattus. Simulated distributions of genetic differentiation were compared to observed data in four independent pairs, each consisting of one population from the plague focus and one from the plague-free zone. We found 22 loci (9% of 249) with higher differentiation in at least two independent population pairs or with combining P-values over the four pairs significant. Among the 22 outlier loci, 16 presented significant association with plague zone (plague focus vs. plague-free zone). Population genetic structure inferred from outlier loci was structured by plague zone, whereas the neutral loci dataset revealed structure by geography (eastern vs. western populations). A phenotype association study revealed that two of the 22 loci were significantly associated with differentiation between dying and surviving rats following experimental plague challenge. The 22 outlier loci identified in this study may undergo plague selective pressure either directly or more probably indirectly due to hitchhiking with selected loci.

Pharmacodynamic study of polymerized porcine hemoglobin (pPolyHb) in a rat model of exchange transfusion.

The objective of the present study is to evaluate the pharmacodynamic properties of polymerized porcine hemoglobin (pPolyHb) in an exchange transfusion model. Each of two groups of rats received a volume of pPolyHb or hetastarch that equalled 120-140% of estimated total blood volume (70 ml/kg) exchange transfusion. The results showed pPolyHb retained hemodynamic stability and exhibited superior volume expansion capability. Furthermore, pPolyHb effectively reverse anaerobic metabolism caused by a large amount of volume exchange. In comparison with hetastarch, pPolyHb increased blood oxygen content and tissue oxygenation. All these properties contribute to a higher effectiveness in sustaining the lives of rats in pPolyHb group.

Is Carriage of Leptospira interrogans by Rats Influenced by the Urban Environment or Population Density?

Leptospira interrogans is one of the most important zoonotic pathogens globally. In urban settings, Norway rats (Rattus norvegicus) are important reservoirs of L. interrogans, but it is unclear how this bacterium is transmitted among rats. Both environmental features and rat population density may determine the prevalence of this pathogen in rat populations as well as the spillover risk to people. While these factors could play an important role in transmission between rats, it is unknown whether such factors influence prevalence among rats at a fine scale. Our objective was to determine if carriage of L. interrogans by rats could be explained by variation in the environment or in rat population density. Rats were live-trapped in a single neighborhood of Vancouver, Canada during two study periods (2011-12; 2016-17) and were tested for L. interrogans. The physical environment of each city block was recorded using a comprehensive, in-person environmental survey. Using generalized linear mixed modelling, we found no evidence of an association between carriage of L. interrogans and environmental features or rat population density, suggesting that these were not the primary drivers of its distribution among rats within this neighborhood. Understanding factors that promote L. interrogans transmission can be used to inform management approaches to minimize public health risks.

The role of subregions of the rat major histocompatibility complex in the rejection and passive enhancement of renal allografts.

The laboratory recombinant haplotype H-1acl of the Norway rat has been used in studies of the rejection and passive enhancement of kidney allografts. While the full H-1a haplotype provoked acute rejection, neither of the isolated subregions, H-1Aa and H-1Ba, did so. It was also found that alloantisera raised against either the H-1Aa or the H-1Ba antigens would enhance the grafts. It is suggested that both MHC subregions contain a histocompatibility locus (i) for kidney (as they do for skin) and that in the genetic combinations studied only incompatibility for both provokes a response sufficient for rejection. In other combinations, however, single region incompatibilities may be sufficient.

L3T4 effector cells in multiple organ-localized autoimmune disease in nude mice grafted with embryonic rat thymus.

Rat thymic grafts reconstituted T cell functions of BALB/c nude (nu/nu) mice to a considerable degree, but multiple organ-localized autoimmune diseases such as oophoritis and thyroiditis generally developed. The effector cell population in this autoimmune model was studied by adoptive transfer of the lesions into syngeneic nude mice. The transfer activity was not diminished when spleen cells were incubated with antiserum against rat cell antigen and C, but the activity was completely vanished by incubation with anti-Thy-1.2 plus C, indicating that the effector cells are T cells of mouse origin. Elimination of the L3T4+ subset virtually abolished the transfer activity, whereas that of the Lyt-2+ subset did not, indicating that the effector cells are L3T4+. Positive selection experiments by FACS also demonstrated that L3T4+ cells, but not Lyt-2+ cells, were capable of inducing the lesion, confirming the results with depletion experiments described above.

T-lymphocyte heterogeneity in the rat: separation of functional subpopulations using a monoclonal antibody.

W3/25 antibody is the monoclonal product of a hybrid cell resulting from the fusion of a mouse myeloma cell line with spleen cells from a mouse immunized with rat thymocytes. Pure clones have been derived, and segregants free of parental myeloma chains have been isolated. Previous studies have shown that this antibody recognizes a subpopulation of T cells among rat thoracic duct lymphocytes. In the work reported here, three T-cell functions were assayed after separating rat thoracic duct lymphocytes on the fluorescence-activated cell sorter on the basis of labeling with W3/25 antibody. Two of the functional activities appeared to be completely segregated by this procedure. Thus, helper cell activity for an anti-hapten plaque-forming cell response was confined to the labeled population, whereas the allogeneic suppressive effect produced in a parental vector F1 adoptive transfer was mediated by cells in the unlabeled fraction. The third function, graft-versus-host activity, was almost entirely contained within the labeled subpopulation. It is concluded that the antigenic determinant recognized by the monoclonal antibody W3/25 is a differentiation marker for T-cell functional subpopulations.

Cell cycle-associated changes in receptors for IgE during growth and differentiation of a rat basophilic leukemia cell line.

The rat basophilic leukemia cell line (RBL-1) showed an inverse relationship between growth rate and expression of receptor activity for IgE. After prolonged exponential growth, the number of receptors per cell stabilized at 4-6 times 10-5. Cells in stationary cultures, which are arrested in the G1 phase of the cell cycle, continued to accumulate up to 0.9-1.7 times 10-6 receptors/cell with no increase in volume. Upon resuspension in fresh medium at low density, these cells were shown to lose up to 70% of the receptor activity within 4 h. Assessment of cultures synchronized by double thymidine block and cells fractionated by centrifugation of a Ficoll gradient indicated that the RBL-1 cells acquire receptors in the G1 phase of the cell cycle. No accumulation of active receptors occurred during the S and G2 phases, though the average cell volume increased. Cell division resulted in a drop in number of receptors per cell while the number of cell-bound receptors in the culture remained unchanged. This indicates that during mitosis receptors were simply distributed to daughter cells.

Subclass restriction of murine antibodies. III. Antigens that stimulate IgG3 in mice stimulate IgG2c in rats.

The IgG subclass distribution of rat antibodies to 13 different antigens was measured. Antibodies to protein and hapten-protein conjugates were predominantly IgG2a. Antigens labeled thymus-independent type 1, based upon responses in mice, stimulated both IgG2b and IgG2c antibodies, but little IgG2a. Polysaccharide and hapten-polysaccharide antigens (thymus-independent type 2) as well as phosphocholine-keyhole limpet hemocyanin, stimulated predominantly IgG2c antibodies. A division of antigens into essentially the same categories has been made on the basis of subclass restriction in mice. Antigens that stimulate IgG2c in rats stimulate IgG3 in mice. Thus, by comparing subclass preference with a variety of antigens, functional analogues among subclasses in different species can be identified.