Overexpression of IκB⍺ modulates NF-κB activation of inflammatory target gene expression.

Cells respond to inflammatory stimuli such as cytokines by activation of the nuclear factor-κB (NF-κB) signalling pathway, resulting in oscillatory translocation of the transcription factor p65 between nucleus and cytoplasm in some cell types. We investigate the relationship between p65 and inhibitor-κB⍺ (IκBα) protein levels and dynamic properties of the system, and how this interaction impacts on the expression of key inflammatory genes. Using bacterial artificial chromosomes, we developed new cell models of IκB⍺-eGFP protein overexpression in a pseudo-native genomic context. We find that cells with high levels of the negative regulator IκBα remain responsive to inflammatory stimuli and maintain dynamics for both p65 and IκBα. In contrast, canonical target gene expression is dramatically reduced by overexpression of IκBα, but can be partially rescued by overexpression of p65. Treatment with leptomycin B to promote nuclear accumulation of IκB⍺ also suppresses canonical target gene expression, suggesting a mechanism in which nuclear IκB⍺ accumulation prevents productive p65 interaction with promoter binding sites. This causes reduced target promoter binding and gene transcription, which we validate by chromatin immunoprecipitation and in primary cells. Overall, we show how inflammatory gene transcription is modulated by the expression levels of both IκB⍺ and p65. This results in an anti-inflammatory effect on transcription, demonstrating a broad mechanism to modulate the strength of inflammatory response.

RAC1B function is essential for breast cancer stem cell maintenance and chemoresistance of breast tumor cells.

Breast cancer stem cells (BCSC) are presumed to be responsible for treatment resistance, tumor recurrence and metastasis of breast tumors. However, development of BCSC-targeting therapies has been held back by their heterogeneity and the lack of BCSC-selective molecular targets. Here, we demonstrate that RAC1B, the only known alternatively spliced variant of the small GTPase RAC1, is expressed in a subset of BCSCs in vivo and its function is required for the maintenance of BCSCs and their chemoresistance to doxorubicin. In human breast cancer cell line MCF7, RAC1B is required for BCSC plasticity and chemoresistance to doxorubicin in vitro and for tumor-initiating abilities in vivo. Unlike Rac1, Rac1b function is dispensable for normal mammary gland development and mammary epithelial stem cell (MaSC) activity. In contrast, loss of Rac1b function in a mouse model of breast cancer hampers the BCSC activity and increases their chemosensitivity to doxorubicin treatment. Collectively, our data suggest that RAC1B is a clinically relevant molecular target for the development of BCSC-targeting therapies that may improve the effectiveness of doxorubicin-mediated chemotherapy.

A kinase-dead Csf1r mutation associated with adult-onset leukoencephalopathy has a dominant inhibitory impact on CSF1R signalling.

Amino acid substitutions in the kinase domain of the human CSF1R gene are associated with autosomal dominant adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP). To model the human disease, we created a disease-associated mutation (pGlu631Lys; E631K) in the mouse Csf1r locus. Homozygous mutation (Csf1rE631K/E631K) phenocopied the Csf1r knockout, with prenatal mortality or severe postnatal growth retardation and hydrocephalus. Heterozygous mutation delayed the postnatal expansion of tissue macrophage populations in most organs. Bone marrow cells from Csf1rE631K/+mice were resistant to CSF1 stimulation in vitro, and Csf1rE631K/+ mice were unresponsive to administration of a CSF1-Fc fusion protein, which expanded tissue macrophage populations in controls. In the brain, microglial cell numbers and dendritic arborisation were reduced in Csf1rE631K/+ mice, as in patients with ALSP. The microglial phenotype is the opposite of microgliosis observed in Csf1r+/- mice. However, we found no evidence of brain pathology or impacts on motor function in aged Csf1rE631K/+ mice. We conclude that heterozygous disease-associated CSF1R mutations compromise CSF1R signalling. We speculate that leukoencephalopathy associated with dominant human CSF1R mutations requires an environmental trigger and/or epistatic interaction with common neurodegenerative disease-associated alleles.

LRRC8A is essential for hypotonicity-, but not for DAMP-induced NLRP3 inflammasome activation.

The NLRP3 inflammasome is a multi-molecular protein complex that converts inactive cytokine precursors into active forms of IL-1ß and IL-18. The NLRP3 inflammasome is frequently associated with the damaging inflammation of non-communicable disease states and is considered an attractive therapeutic target. However, there is much regarding the mechanism of NLRP3 activation that remains unknown. Chloride efflux is suggested as an important step in NLRP3 activation, but which chloride channels are involved is still unknown. We used chemical, biochemical, and genetic approaches to establish the importance of chloride channels in the regulation of NLRP3 in murine macrophages. Specifically, we identify LRRC8A, an essential component of volume-regulated anion channels (VRAC), as a vital regulator of hypotonicity-induced, but not DAMP-induced, NLRP3 inflammasome activation. Although LRRC8A was dispensable for canonical DAMP-dependent NLRP3 activation, this was still sensitive to chloride channel inhibitors, suggesting there are additional and specific chloride sensing and regulating mechanisms controlling NLRP3.

Inflammation is a critical part of a healthy immune system, which protects us against harmful pathogens (such as bacteria or viruses) and works to restore damaged tissues. In the immune cells of our body, the inflammatory process can be activated through a group of inflammatory proteins that together are known as the NLRP3 inflammasome complex. While inflammation is a powerful mechanism that protects the human body, persistent or uncontrolled inflammation can cause serious, long-term damage. The inappropriate activation of the NLRP3 inflammasome has been implicated in several diseases, including Alzheimer's disease, heart disease, and diabetes. The NLRP3 inflammasome can be activated by different stimuli, including changes in cell volume and exposure to either molecules produced by damaged cells or toxins from bacteria. However, the precise mechanism through which the NLRP3 becomes activated in response to these stimuli was not clear. The exit of chloride ions from immune cells is known to activate the NLRP3 inflammasome. Chloride ions exit the cell through proteins called anion channels, including volume-regulated anion channels (VRACs), which respond to changes in cell volume. Green et al. have found that, in immune cells from mice grown in the lab called macrophages, VRACs are the only chloride channels involved in activating the NLRP3 inflammasome when the cell's volume changes. However, when the macrophages are exposed to molecules produced by damaged cells or toxins from bacteria, Green et al. discovered that other previously unidentified chloride channels are involved in activating the NLRP3 inflammasome. These results suggest that it might be possible to develop drugs to prevent the activation of the NLRP3 inflammasome that selectively target specific sets of chloride channels depending on which stimuli are causing the inflammation. Such a selective approach would minimise the side effects associated with drugs that generically suppress all NLRP3 activity by directly binding to NLRP3 itself. Ultimately, this may help guide the development of new, targeted anti-inflammatory drugs that can help treat the symptoms of a variety of diseases in humans.

A Transgenic Line That Reports CSF1R Protein Expression Provides a Definitive Marker for the Mouse Mononuclear Phagocyte System.

The proliferation, differentiation, and survival of cells of the mononuclear phagocyte system (MPS; progenitors, monocytes, macrophages, and classical dendritic cells) are controlled by signals from the M-CSF receptor (CSF1R). Cells of the MPS lineage have been identified using numerous surface markers and transgenic reporters, but none is both universal and lineage restricted. In this article, we report the development and characterization of a CSF1R reporter mouse. A FusionRed (FRed) cassette was inserted in-frame with the C terminus of CSF1R, separated by a T2A-cleavable linker. The insertion had no effect of CSF1R expression or function. CSF1R-FRed was expressed in monocytes and macrophages and absent from granulocytes and lymphocytes. In bone marrow, CSF1R-FRed was absent in lineage-negative hematopoietic stem cells, arguing against a direct role for CSF1R in myeloid lineage commitment. It was highly expressed in marrow monocytes and common myeloid progenitors but significantly lower in granulocyte-macrophage progenitors. In sections of bone marrow, CSF1R-FRed was also detected in osteoclasts, CD169+ resident macrophages, and, consistent with previous mRNA analysis, in megakaryocytes. In lymphoid tissues, CSF1R-FRed highlighted diverse MPS populations, including classical dendritic cells. Whole mount imaging of nonlymphoid tissues in mice with combined CSF1R-FRed/Csf1r-EGFP confirmed the restriction of CSF1R expression to MPS cells. The two markers highlight the remarkable abundance and regular distribution of tissue MPS cells, including novel macrophage populations within tendon and skeletal muscle and underlying the mesothelial/serosal/capsular surfaces of every major organ. The CSF1R-FRed mouse provides a novel reporter with exquisite specificity for cells of the MPS.

Cell-specific conditional deletion of interleukin-1 (IL-1) ligands and its receptors: a new toolbox to study the role of IL-1 in health and disease.

The pro-inflammatory cytokine interleukin-1 (IL-1) plays a key role in many physiological processes and during the inflammatory and immune response to most common diseases. IL-1 exists as two agonists, IL-1α and IL-1ß that bind to the only signaling IL-1 type 1 receptor (IL-1R1), while a second decoy IL-1 type 2 receptor (IL-1R2) binds both forms of IL-1 without inducing cell signaling. The field of immunology and inflammation research has, over the past 35 years, unraveled many mechanisms of IL-1 actions, through in vitro manipulation of the IL-1 system or by using genetically engineered mouse models that lack either member of the IL-1 family in ubiquitous constitutive manner. However, the limitation of global mouse knockout technology has significantly hampered our understanding of the precise mechanisms of IL-1 actions in animal models of disease. Here we report and review the recent generation of new conditional mouse mutants in which exons of Il1a, Il1b, Il1r1, and Il1r2 genes flanked by loxP sites (fl/fl) can be deleted in cell-/tissue-specific constitutive or inducible manner by Cre recombinase expression. Hence, IL-1αfl/fl, IL-1ßfl/fl, IL-1R1fl/fl, and IL-1R2fl/fl mice constitute a new toolbox that will provide a step change in our understanding of the cell-specific role of IL-1 and its receptor in health and disease and the potential development of targeted IL-1 therapies.

Cardiac mitochondrial function depends on BUD23 mediated ribosome programming.

Efficient mitochondrial function is required in tissues with high energy demand such as the heart, and mitochondrial dysfunction is associated with cardiovascular disease. Expression of mitochondrial proteins is tightly regulated in response to internal and external stimuli. Here we identify a novel mechanism regulating mitochondrial content and function, through BUD23-dependent ribosome generation. BUD23 was required for ribosome maturation, normal 18S/28S stoichiometry and modulated the translation of mitochondrial transcripts in human A549 cells. Deletion of Bud23 in murine cardiomyocytes reduced mitochondrial content and function, leading to severe cardiomyopathy and death. We discovered that BUD23 selectively promotes ribosomal interaction with low GC-content 5'UTRs. Taken together we identify a critical role for BUD23 in bioenergetics gene expression, by promoting efficient translation of mRNA transcripts with low 5'UTR GC content. BUD23 emerges as essential to mouse development, and to postnatal cardiac function.

Cells need to make proteins to survive, so they have protein-making machines called ribosomes. Ribosomes are themselves made out of proteins and RNA (a molecule similar to DNA), and they are assembled by other proteins that bring ribosomal components together and modify them until the ribosomes are functional.Mitochondria are compartments in the cell that are in charge of providing it with energy. To do this they require several proteins produced by the ribosomes. If not enough mitochondrial proteins are made, mitochondria cannot provide enough energy for the cell to survive.One of the proteins involved in modifying ribosomes so they are functional is called BUD23. People with certain diseases, such as Williams-Beuren syndrome, do not make enough BUD23; but it was unknown what specific effects resulted from a loss of BUD23.To answer this question, Baxter et al. first genetically removed BUD23 from human cells, and then checked what happened to protein production. They found that ribosomes in human cells with no BUD23 were different than in normal cells, and that cells without BUD23 produced different proteins, which did not always perform their roles correctly. Proteins in the mitochondria are one of the main groups affected by the absence of BUD23. To determine what effects these modified mitochondrial proteins would have in an animal, Baxter et al. genetically modified mice so that they no longer produced BUD23. These mice developed heart problems caused by their mitochondria not working correctly and being unable to provide the energy the heart cells needed, eventually leading to heart failure. Heart problems are common in people with Williams-Beuren syndrome.Many diseases arise when a person's mitochondria do not work properly, but it is often unclear why. These experiments suggest that low levels of BUD23 or faulty ribosomes may be causing mitochondria to work poorly in some of these diseases, which could lead to the development of new therapies.

Fibroblast-specific deletion of interleukin-1 receptor-1 reduces adverse cardiac remodeling following myocardial infarction.

It has been hypothesized that interleukin-1alpha (IL-1α) is released from damaged cardiomyocytes following myocardial infarction (MI) and activates cardiac fibroblasts via its receptor (IL-1R1) to drive the early stages of cardiac remodeling. This study aimed to definitively test this hypothesis using cell type-specific IL-1α and IL-1R1 knockout (KO) mouse models. A floxed Il1α mouse was created and used to generate a cardiomyocyte-specific IL-1α KO mouse line (MIL1AKO). A tamoxifen-inducible fibroblast-specific IL-1R1 hemizygous KO mouse line (FIL1R1KO) was also generated. Mice underwent experimental MI (permanent left anterior descending coronary artery ligation) and cardiac function was determined 4 weeks later by conductance pressure-volume catheter analysis. Molecular markers of remodeling were evaluated at various time points by real-time RT-PCR and histology. MIL1AKO mice showed no difference in cardiac function or molecular markers of remodeling post-MI compared with littermate controls. In contrast, FIL1R1KO mice showed improved cardiac function and reduced remodeling markers post-MI compared with littermate controls. In conclusion, these data highlight a key role for the IL-1R1/cardiac fibroblast signaling axis in regulating post-MI remodeling and provide support for the continued development of anti-IL-1 therapies for improving cardiac function after MI. Cardiomyocyte-derived IL-1α was not an important contributor to post-MI remodeling in this model.

Generation of induced pluripotent stem cells from virus-free in vivo reprogramming of BALB/c mouse liver cells.

The in vivo cell reprogramming of terminally differentiated somatic cells to a pluripotent state by the ectopic expression of defined transcription factors has been previously shown in the BALB/c mouse liver upon plasmid DNA injection with no teratoma formation in the host tissue. Here, we hypothesized that the reprogrammed cells could be extracted from the tissue and cultured in vitro. We called these cells in vivo induced pluripotent stem (i(2)PS) cells because they showed pluripotent characteristics equivalent to a standard mouse ES cell line (E14TG2A). The pluripotent character of i(2)PS cells was determined by a battery of morphological, molecular and functional assays, including their contribution to adult tissues of chimeric mice upon blastocyst injection. These observations further confirm that terminally differentiated somatic cells in wild type, adult animals can be reprogrammed in vivo using virus-free methodologies. The reprogrammed cells can generate in vitro stem cell colonies that exhibit pluripotency similar to ES cells with numerous implications for the application of in vivo reprogramming for tissue regenerative purposes.

Immunity to gastrointestinal nematodes: mechanisms and myths.

Immune responses to gastrointestinal nematodes have been studied extensively for over 80 years and intensively investigated over the last 30-40 years. The use of laboratory models has led to the discovery of new mechanisms of protective immunity and made major contributions to our fundamental understanding of both innate and adaptive responses. In addition to host protection, it is clear that immunoregulatory processes are common in infected individuals and resistance often operates alongside modulation of immunity. This review aims to discuss the recent discoveries in both host protection and immunoregulation against gastrointestinal nematodes, placing the data in context of the specific life cycles imposed by the different parasites studied and the future challenges of considering the mucosal/immune axis to encompass host, parasite, and microbiome in its widest sense.

Experimental stroke-induced changes in the bone marrow reveal complex regulation of leukocyte responses.

Stroke induces a systemic response that involves rapid activation of inflammatory cascades, followed later by immunodepression. Experimental stroke-induced responses in the bone marrow, which is the primary source of circulating monocytes and granulocytes, have not been investigated previously. We show that cerebral ischaemia induced early (4 hours) release of CXCR2-positive granulocytes from the bone marrow, which was associated with rapid systemic upregulation of CXCL1 (a ligand for CXCR2) and granulocyte-colony-stimulating factor, a key cytokine involved in the mobilisation of bone marrow leukocytes. This process involves rapid activation of nuclear factor-κB and p38 mitogen-activated protein kinase in bone marrow myeloid cells. T-cell numbers in the bone marrow increased after stroke, and bone marrow cells did not show suppressed cytokine response to bacterial endotoxin stimulation in vitro. Stroke-induced laterality observed in the brain stem and in the bone marrow indicates direct involvement of the autonomic nervous system in stroke-induced cell mobilisation. We also show that systemic inflammatory changes and leukocyte responses in the bone marrow are profoundly affected by both anaesthetic and surgical stress. We conclude that stroke influences leukocyte responses in the bone marrow through multiple mechanisms and suggest that preclinical studies should take into consideration the effect of surgical manipulation in experimental models of stroke.

Helminth products bypass the need for TSLP in Th2 immune responses by directly modulating dendritic cell function.

Thymic stromal lymphopoietin (TSLP) is an interleukin (IL)-7-like cytokine, mainly expressed by epithelial cells, and key to the development of allergic responses. The well-documented involvement of TSLP in allergy has led to the conviction that TSLP promotes the development of inflammatory Th2 cell responses. However, we now report that the interaction of TSLP with its receptor (TSLPR) has no functional impact on the development of protective Th2 immune responses after infection with 2 helminth pathogens, Heligmosomoides polygyrus and Nippostrongylus brasiliensis. Mice deficient in the TSLP binding chain of the TSLPR (TSLPR(-/-)) exhibited normal Th2 cell differentiation, protective immunity and memory responses against these two distinct rodent helminths. In contrast TSLP was found to be necessary for the development of protective Th2 responses upon infection with the helminth Trichuris muris (T. muris). TSLP inhibited IL-12p40 production in response to T. muris infection, and treatment of TSLPR(-/-) animals with neutralizing anti-IL-12p40 monoclonal antibody (mAb) was able to reverse susceptibility and attenuate IFN-gamma production. We additionally demonstrated that excretory-secretory (ES) products from H. polygyrus and N. brasiliensis, but not T. muris, were capable of directly suppressing dendritic cell (DC) production of IL-12p40, thus bypassing the need for TSLP. Taken together, our data show that the primary function of TSLP is to directly suppress IL-12 secretion, thus supporting Th2 immune responses.

IL-1-dependent, IL-1R1-independent resistance to gastrointestinal nematodes.

IL-1 null mice are unable to expel the intestinal nematode Trichuris muris; whereas WT littermates exhibit sterile immunity. Intriguingly the essential signalling components IL-1R1 and IL-1R accessory protein (AcP) are dispensable for expulsion of this parasite. IL-1 is thus critical for CD4(+) Th2-mediated immunity to T. muris; however, this action is independent of the established IL-1 signalling receptor. We also present data demonstrating that both IL-1alpha and IL-1beta induce measurable effects on T. muris primed cells isolated from IL-1R1 or IL-1R AcP null mice. MLN cells from these mice restimulated with parasite antigen proliferated at a greater rate and produced more cytokines in response to exogenous IL-1. This ability to respond to IL-1 was restricted to these parasite-primed cells and importantly was not evident in cells from naïve gene null mice. These in vitro data are consistent with the observed ability of mice with compromised IL-1 signalling to expel the parasite, bolstering the premise that an alternative IL-1 signalling mechanism is accessible in the context of an intestinal helminth-driven Th2 immune response.

IL-33, a potent inducer of adaptive immunity to intestinal nematodes.

IL-33 (IL-1F11) binds ST2 (IL-1R4), both of which are associated with optimal CD4(+) Th2 polarization. Exogenous IL-33 drives induction of Th2-associated cytokines and associated pathological changes within the gut mucosa. Th2 polarization is also a prerequisite to expulsion of the intestinal-dwelling nematode Trichuris muris. In this study, we demonstrate that IL-33 mRNA is expressed early during parasite infection and susceptible mice can be induced to expel the parasite by a regime of exogenous IL-33 administration. IL-33 prevents an inappropriate parasite-specific Th1-polarized response and induces IL-4, IL-9, and IL-13. This redirection requires the presence of T cells and must occur at the initiation of the response to the pathogen. Interestingly, exogenous IL-33 also induced thymic stromal lymphopoietin mRNA within the infected caecum, an epithelial cell-restricted cytokine essential for the generation of Th2-driven parasite immunity. IL-33 also acts independently of T cells, altering intestinal pathology in chronically infected SCID mice, leading to an increased crypt length and intestinal epithelial cell proliferation, but reducing goblet cell hyperplasia. Thus, the ability of IL-33 to induce Th2 responses has functional relevance in the context of intestinal helminth infection, particularly during the initiation of the response.

Intraepithelial NK cell-derived IL-13 induces intestinal pathology associated with nematode infection.

IL-13 is a Th2-derived cytokine associated with pathological changes in asthma and ulcerative colitis. Moreover, it plays a major role in the control of gut nematode infection and associated immunopathology. The current paradigm is that these effects are due to T cell-derived IL-13. We show in this study that an innate source of IL-13, the intraepithelial NK cell, is responsible for the disruption of intestinal tissue architecture and induction of goblet cell hyperplasia that characterizes infection with the intestinal helminth Trichinella spiralis. IL-13 or IL-4Ralpha (but not IL-4) null mice failed to induce intestinal pathology. Unexpectedly, SCID and athymic mice developed the same pathology found in immunocompetent mice following infection. Moreover, immunodeficient mice expressed IL-13 in the intestine, and abnormal mucosal pathology was reduced by in vivo administration of a soluble IL-13 antagonist. IL-13 expression was induced in non-T intraepithelial CD3- NK cells. Epithelial cells expressed the IL-13 signaling receptor, IL-13Ralpha1, and after infection, IL-4Ralpha. Furthermore, the soluble IL-13 decoy receptor IL-13Ralpha2, which regulates IL-13 responses, was also induced upon infection. These data provide the first evidence that intestinal tissue restructuring during helminth infection is an innate event dependent on IL-13 production by NK cells resident in the epithelium of the intestine.

Accelerated intestinal epithelial cell turnover: a new mechanism of parasite expulsion.

The functional integrity of the intestinal epithelial barrier forms a major defense against invading pathogens, including gastrointestinal-dwelling nematodes, which are ubiquitous in their distribution worldwide. Here, we show that an increase in the rate of epithelial cell turnover in the large intestine acts like an "epithelial escalator" to expel Trichuris and that the rate of epithelial cell movement is under immune control by the cytokine interleukin-13 and the chemokine CXCL10. This host protective mechanism against intestinal pathogens has implications for our wider understanding of the multifunctional role played by intestinal epithelium in mucosal defense.

WSX-1: a key role in induction of chronic intestinal nematode infection.

Chronic infection by the gastrointestinal nematode Trichuris muris in susceptible AKR mice, which mount a Th1 response, is associated with IL-27p28 expression in the cecum. In contrast to wild-type mice, mice that lack the WSX-1/IL-27R gene fail to harbor a chronic infection, having significantly lower Th1 responses. The lower level of Ag-specific IFN-gamma-positive cells in WSX-1 knockout (KO) mice was found to be CD4(+) T cell specific, and the KO mice also had increased levels of IL-4-positive CD4(+) T cells. Polyclonal activation of mesenteric lymph node cells from naive WSX-1 KO or wild-type mice demonstrated that there was no inherent defect in the production of IFN-gamma by CD4(+) T cells, suggesting the decrease in these cells seen in infected WSX-1 KO mice is an in vivo Ag-driven effect. IL-12 treatment of WSX-1 KO mice failed to rescue the type 1 response, resulting in unaltered type-2-driven resistance. Infection of WSX-1 KO mice was also associated with a reduction of IL-27/WSX-1 downstream signaling gene expression within the cecum. These studies demonstrate an important role for WSX-1 signaling in the promotion of type 1 responses and chronic gastrointestinal nematode infection.

Assessment of cumulative allergen-activated lymph node cell proliferation using flow cytometry.

The murine local lymph node assay (LLNA) is a method for the prospective identification of chemical contact allergens. The current validated protocol assesses lymphocyte proliferation induced in the draining lymph node as a function of in situ incorporation of radiolabeled thymidine. We have explored the potential utility of an alternative nonradioisotopic marker of cell division, the cytoplasmic dye carboxyfluoresein succinimidyl ester (CFSE). Using this method, the cell phenotype and the number of divisions each cell has undergone can be tracked using flow cytometry. BALB/c strain mice were exposed topically to various concentrations of the contact allergens 2,4-dinitrochlorobenzene (DNCB), oxazolone (ox) or hexyl cinnamic aldehyde (HCA), or to the nonsensitizing skin irritant methyl salicylate (MS). Five days later, lymph node cells (LNC) were labeled with CFSE, cultured for 96 h, then incubated with fluorescent labeled anti-CD4 (T helper) and -CD8 (T cytotoxic) cell antibodies, and proliferating CD4+ and CD8+ cells analyzed by flow cytometry. In LNC populations derived from vehicle-treated animals, less than 1% of either cell population had undergone one cell division or more. Topical exposure to MS (2.5 to 20%) did not increase the frequencies of proliferating cells. Exposure to all three allergens, however, resulted in a marked increase in the percentages of both CD4+ and CD8+ cells undergoing division, with up to 5% and 3% of these cells, respectively, proliferating in response to DNCB and oxazolone, and with lower levels of proliferation stimulated by HCA. These preliminary data suggest that this method may be applied to provide the basis of a nonradioisotopic end point for the LLNA, particularly for the identification of potent contact allergens.

Effects of ageing on the immunoregulation of parasitic infection.

The plethora of changes associated with immunosenescence radically alters virtually all aspects of immune responsiveness. How this transformation effects resolution of an infectious challenge is addressed in this study. A well-established infection model was used; Trichuris muris, a cecum-dwelling helminth, is natural to mice, and infection in different strains results in clearly polarized responses. A dominating T helper 2 (Th2) response orchestrates immunity, whereas a Th1 response will result in susceptibility. Mice between 19 and 28 months old were more susceptible to infection, whereas 3-month-old mice of the same strain demonstrated the resistant phenotype. The cytokine response made by these aged mice was clearly altered at the site of infection, and within the local draining lymph nodes higher Th1 and lower Th2 cytokine levels were found, both at the protein and RNA level. Confirming these changes, aged mice also showed a delayed parasite-specific immunoglobulin G1 response and intestinal mastocytosis, both of which are driven by Th2 cytokines. To address possible causes of the observed immune deviation, purified CD4 cells from both young and aged mice were stimulated in vitro. Cells from aged mice did not respond to stimulation via CD28 and in vitro were less able to proliferate and polarize into Th2 cells; Th1 polarization was found to be normal. Together these data suggest that changes in cytokine phenotype, particularly CD4 cells, contribute to the observed age-associated switch from T. muris resistance to susceptibility.