FURIN regulates cytotoxic T-lymphocyte effector function and memory cell transition in mice.

The proprotein convertase subtilisin/kexins (PCSKs) regulate biological actions by cleaving immature substrate proteins. The archetype PCSK, FURIN, promotes the pathogenicity of viruses by proteolytically processing viral proteins. FURIN has also important regulatory functions in both innate and adaptive immune responses but its role in the CD8+ CTLs remains enigmatic. We used a T-cell-specific FURIN deletion in vivo to demonstrate that FURIN promotes host response against the CTL-dependent lymphocytic choriomeningitis virus by virtue of restricting viral burden and augmenting interferon gamma (IFNG) production. We also characterized Furin KO CD8+ T cells ex vivo, including after their activation with FURIN regulating cytokines IL12 or TGFB1. Furin KO CD8+ T cells show an inherently activated phenotype characterized by the upregulation of effector genes and increased frequencies of CD44+ , TNF+ , and IFNG+ cells. In the activated CTLs, FURIN regulates the productions of IL2, TNF, and GZMB and the genes associated with the TGFBR-signaling pathway. FURIN also controls the expression of Eomes, Foxo1, and Bcl6 and the levels of ITGAE and CD62L, which implies a role in the development of CTL memory. Collectively, our data suggest that the T-cell expressed FURIN is important for host responses in viral infections, CTL homeostasis/activation, and memory development.

Immunomodulatory Functions of Adipose Mesenchymal Stromal/Stem Cell Derived From Donors With Type 2 Diabetes and Obesity on CD4 T Cells.

For adipose stromal/stem cell (ASCs)-based immunomodulatory therapies, it is important to study how donor characteristics, such as obesity and type 2 diabetes (T2D), influence ASCs efficacy. Here, ASCs were obtained from 2 groups, donors with T2D and obesity (dASCs) or nondiabetic donors with normal-weight (ndASCs), and then cultured with anti-CD3/CD28-stimulated allogeneic CD4 T cells. ASCs were studied for the expression of the immunomodulators CD54, CD274, and indoleamine 2, 3 dioxygenase 1 (IDO) in inflammatory conditions. CD4 T cells cultured alone or in cocultures were assessed to evaluate proliferation, activation marker surface expression, apoptosis, the regulatory T cells (Tregs; CD4+ CD25high FOXP3+) frequency, and intracellular cytokine expression using flow cytometry. Modulation of T-cell subset cytokines was explored via ELISA. In inflammatory conditions, the expression of CD54, CD274, and IDO was significantly upregulated in ASCs, with no significant differences between ndASCs and dASCs. dASCs retained the potential to significantly suppress CD4 T-cell proliferation, with a slightly weaker inhibitory effect than ndASCs, which was associated with significantly reduced abilities to decrease IL-2 production and increase IL-8 levels in cocultures. Such attenuated potentials were significantly correlated with increasing body mass index. dASCs and ndASCs comparably reduced CD4 T-cell viability, HLA-DR expression, and interferon-gamma production and conversely increased CD69 expression, the Tregs percentage, and IL-17A production. Considerable amounts of the immunomodulators prostaglandin E2 (PGE2) and IL-6 were detected in the conditioned medium of cocultures. These findings suggest that ASCs obtained from donors with T2D and obesity are receptive to the inflammatory environment and able to modulate CD4 T cells accordingly.

Comparison of the effect of autoclaved and non-autoclaved live soil exposure on the mouse immune system : Effect of soil exposure on immune system.

BACKGROUND: . Lack of exposure to the natural microbial diversity of the environment has been linked to dysregulation of the immune system and numerous noncommunicable diseases, such as allergies and autoimmune disorders. Our previous studies suggest that contact with soil material, rich in naturally occurring microbes, could have a beneficial immunoregulatory impact on the immune system in mice and humans. However, differences in the immunomodulatory properties of autoclaved, sterile soil material and non-autoclaved, live soil material have not been compared earlier. RESULTS: . In this study, we exposed C57BL/6 mice to autoclaved and live soil powders that had the same rich microbiota before autoclaving. We studied the effect of the soil powders on the mouse immune system by analyzing different immune cell populations, gene expression in the gut, mesenteric lymph nodes and lung, and serum cytokines. Both autoclaved and live soil exposure were associated with changes in the immune system. The exposure to autoclaved soil resulted in higher levels of Rorγt, Inos and Foxp3 expression in the colon. The exposure to live soil was associated with elevated IFN-γ concentration in the serum. In the mesenteric lymph node, exposure to live soil reduced Gata3 and Foxp3 expression, increased the percentage of CD8 + T cells and the expression of activation marker CD80 in XCR1+SIRPα- migratory conventional dendritic cell 1 subset. CONCLUSIONS: . Our results indicate that exposure to the live and autoclaved soil powders is not toxic for mice. Exposure to live soil powder slightly skews the immune system towards type 1 direction which might be beneficial for inhibiting type 2-related inflammation. Further studies are warranted to quantify the impact of this exposure in experimental type 2 inflammation.

IL-4, IL-13 and IFN-γ -induced genes in highly purified human neutrophils.

Interleukin (IL)-4 and IL-13 are related cytokines with well-known specific roles in type 2 immune response. However, their effects on neutrophils are not completely understood. For this, we studied human primary neutrophil responses to IL-4 and IL-13. Neutrophils are dose-dependently responsive to both IL-4 and IL-13 as indicated by signal transducer and activator of transcription 6 (STAT6) phosphorylation upon stimulation, with IL-4 being more potent inducer of STAT6. IL-4-, IL-13- and Interferon (IFN)-γ-stimulated gene expression in highly purified human neutrophils induced both overlapping and unique gene expression in highly purified human neutrophils. IL-4 and IL-13 specifically regulate several immune-related genes, including IL-10, tumor necrosis factor (TNF) and leukemia inhibitory factor (LIF), while type1 immune response-related IFN-γ induced gene expression related for example, to intracellular infections. In analysis of neutrophil metabolic responses, oxygen independent glycolysis was specifically regulated by IL-4, but not by IL-13 or IFN-γ, suggesting specific role for type I IL-4 receptor in this process. Our results provide a comprehensive analysis of IL-4, IL-13 and IFN-γ -induced gene expression in neutrophils while also addressing cytokine-mediated metabolic changes in neutrophils.

Positive Francisella tularensis meningitis outcome despite delayed identification: a case report.

Francisella tularensis is a Gram-negative bacteria, that may cause a zoonotic disease, tularemia. Here, we describe a patient case, where a previously healthy young woman in Northern Finland contacted health care because of fever and headache. Due to the symptoms and lack of further diagnostic tools in primary health care, she was transferred to University Hospital (UH) where ampicillin and ceftriaxone was given empirically. A cerebrospinal fluid sample (CSF) was drawn showing small Gram-negative rods that grew on chocolate agar after 2 days of incubation. Matrix-assisted laser-desorption-ionization time of-flight (Maldi-tof) did not provide identification, but the bacteria was interpreted as sensitive to ciprofloxacin and the treatment was changed to ciprofloxacin. During the time the patient was infected, there were several positive tularemia samples found in the area. Therefore, an in house tularemia nucleic acid method (PCR) was used on the bacterial culture. Additionally, 16S rDNA sequencing was performed and these methods identified the bacteria as F. tularensis. Fortunately, the patient recovered completely with ciprofloxacin and was discharged without any complications. Our case underlines the need to understand the limits of specific diagnostic methods, such as Maldi-tof, used in clinical laboratory settings. It also highlights the need of both clinicians and laboratory staff to be aware of the many clinical presentations of tularemia when working in an endemic area.

Impact of COVID-19 Pandemic on the Incidence of Sexually Transmitted Infections in Northern Finland in 2019 to 2022.

The coronavirus SARS-CoV-2 (COVID-19) pandemic led to major restrictions in daily life and social contacts in Finland in March 2020. The effect of these restrictions on sexually transmitted infections (STIs) is unclear. The aim of this study was to analyse the incidence and positive rates of sexually transmitted infections in Northern Finland between 2020 and 2021 and compare these with the years prior to the pandemic. Numbers of positive Chlamydia trachomatis, HIV and hepatitis C samples were lower in 2020 to 2021 than in previous years, whereas more gonorrhoea and syphilis was found during pandemic than in previous years. The number of new cases of C. trachomatis reported each month decreased in the first months of the pandemic, but exceeded the prior pandemic-level in autumn 2020. When the mean positive sample rates were compared with the years 2015 to 2019, there was a significant decrease in positive C. trachomatis (p < 0.001) and hepatitis C (p < 0.001) sample rates in both 2020 and 2021. The positive rates for Treponema pallidum in 2020 did not differ significantly (p = 0.38) from previous years. In conclusion, these results show that sexually transmitted infections occurred despite recommendations for social distancing during the COVID-19 pandemic. Thus, easy access to STI testing should always be available, even during exceptional circumstances.

The transcription factor GATA3 actively represses RUNX3 protein-regulated production of interferon-gamma.

The transcription factor GATA3 is crucial for the differentiation of naive CD4(+) T cells into T helper 2 (Th2) cells. Here, we show that deletion of Gata3 allowed the appearance of interferon-gamma (IFN-gamma)-producing cells in the absence of interleukin-12 (IL-12) and IFN-gamma. Such IFN-gamma production was transcription factor T-bet independent. Another T-box-containing transcription factor Eomes, but not T-bet, was induced both in GATA3-deficient CD4(+) T cells differentiated under Th2 cell conditions and in Th2 cells with enforced Runx3 expression, contributing to IFN-gamma production. GATA3 overexpression blocked Runx3-mediated Eomes induction and IFN-gamma production, and GATA3 protein physically interacted with Runx3 protein. Furthermore, we found that Runx3 directly bound to multiple regulatory elements of the Ifng gene and that blocking Runx3 function in either Th1 or GATA3-deficient "Th2" cells results in diminished IFN-gamma production by these cells. Thus, the Runx3-mediated pathway, actively suppressed by GATA3, induces IFN-gamma production in a STAT4- and T-bet-independent manner.

IL-7Rα Expression Regulates Murine Dendritic Cell Sensitivity to Thymic Stromal Lymphopoietin.

Thymic stromal lymphopoietin (TSLP) and IL-7 are related cytokines that mediate growth and differentiation events in the immune system. They signal through IL-7Rα-containing receptors. Target cells of TSLP in Th2 responses include CD4 T cells and dendritic cells (DCs). Although it has been reported that expression of TSLP receptor (TSLPR) on CD4 T cells is required for OVA-induced lung inflammation, DCs have also been shown to be target cells of TSLP. In this study, we show that murine ex vivo splenic DCs are unresponsive to TSLP, as they fail to phosphorylate STAT5, but in vitro overnight culture, especially in presence of IL-4, renders DCs responsive to both TSLP and IL-7. This induced responsiveness is accompanied by dramatic upregulation of IL-7Rα on DCs with little change in expression of TSLPR or of γc In splenic DCs, the induction of IL-7Rα occurs mainly in CD8- DCs. In vivo, we found that IL-4 has a differential regulatory role on expression of IL-7Rα depending on the cell type; IL-4 decreases IL-7Rα expression on CD4 T cells whereas it upregulates the expression on DCs. Our results indicate that the induction of IL-7Rα expression on DCs is critical for TSLP responsiveness and that IL-4 can upregulate IL-7Rα on DCs.

CD27- IgD- B cell memory subset associates with inflammation and frailty in elderly individuals but only in males.

BACKGROUND: Immunosenescence, i.e. the aging-associated decline of the capacity of the immune system, is characterized by several distinct changes in the number and functions of the immune cells. In the case of B cells, the total number of CD19+ B cells is lower in the blood of elderly individuals than in the younger ones. CD19+ B cell population contains several subsets, which are commonly characterized by the presence of CD27 and IgD molecules, i.e. naïve B cells (CD27- IgD+), IgM memory (CD27+ IgD+), switched memory (CD27+ IgD-) and late memory (CD27- IgD-). This late memory, double negative, population represents cells which are nondividing, but are still able to produce inflammatory mediators and in this way maybe contributing to the aging-associated inflammation, inflammaging. Here we have focused on the role of these B cell subsets in elderly individuals, nonagenarians, in the regulation of inflammation and inflammation-associated decline of bodily functions. As the biological aging process demonstrates gender-specific characteristics, the analyses were performed separately in males and female. RESULTS: A subcohort of The Vitality 90+ study (67 nonagenarians, 22/45 males/females and 40 young controls, 13/27 males/females) was used. Flow cytometric analysis indicated that the total percentage of the CD19+ cells was ca. 50% lower in the nonagenarians than in the controls in both genders. The proportions of these four B cell subsets within the CD19+ populations were very similar in young and old individuals. Thus, it seems that the aging-associated decline of the total CD19+ cells affects similarly all these B cell subsets. To analyze the role of these subsets in the regulation of inflammation, the correlation with IL-6 levels was calculated. A significant correlation was observed only with the percentage of CD27- IgD- cells and only in males. As inflammation is associated with aging-associated functional performance and frailty, the correlations with the Barthel index and frailty score was analyzed. Again, only the CD27- IgD- population demonstrated a strong male-specific correlation. CONCLUSIONS: These data show that the CD27- IgD- B cell subset demonstrates a strong pro-inflammatory effect in nonagenarians, which significantly associates with the decline of the bodily functions. However, this phenomenon is only observed in males.

NKG2D gene variation and susceptibility to viral bronchiolitis in childhood.

BACKGROUND: Genetic factors associated with bronchiolitis are inadequately characterized. We therefore inspected a selected subpopulation of our previous genome-wide association study (GWAS) of bronchiolitis for overlap with known quantitative trait loci (QTLs) to identify susceptibility loci that potentially affect mRNA and protein levels. METHODS: GWAS included a Finnish-Swedish case-control population (n = 187), matched for age and site. We integrated GWAS variants (p < 10-4) with QTL data. We subsequently verified allele-specific expression of identified QTLs by flow cytometry. Association of the resulting candidate loci with bronchiolitis was tested in three additional cohorts from Finland and Denmark (n = 1201). RESULTS: Bronchiolitis-susceptibility variant rs10772271 resided within QTLs previously associated with NKG2D (NK group 2, member D) mRNA and protein levels. Flow cytometric analysis confirmed the association with protein level in NK cells. The GWAS susceptibility allele (A) of rs10772271 (odds ratio [OR] = 2.34) corresponded with decreased NKG2D expression. The allele was nominally associated with bronchiolitis in one Finnish replicate (OR = 1.50), and the other showed directional consistency (OR = 1.43). No association was detected in Danish population CONCLUSIONS: The bronchiolitis GWAS susceptibility allele was linked to decreased NKG2D expression in the QTL data and in our expression analysis. We propose that reduced NKG2D expression predisposes infants to severe bronchiolitis.

Challenges in investigation of diabetes-related aviation fatalities-an analysis of 1491 subsequent aviation fatalities in USA during 2011-2016.

Diabetes mellitus (DM) could cause pilot incapacitation and result in aviation fatalities. The mechanisms could be directly as a consequence of acute hypoglycemia/subacute diabetic ketoacidosis (DKA) or indirectly as an acute cardiovascular event by contributing to the development of atherosclerosis in coronary or carotid and cerebral arteries. In this study, DM-related fatal flight accidents in the US National Transport Bureau's database between years 2011-2016 were analyzed with special emphasis on postmortem (PM) glucose levels and correlation of toxicological reports with anamnestic information on DM. Additionally, autopsy results on coronary arteries were reviewed. In 43 out of 1491 (~ 3%) fatal accidents pilots had DM. Postmortem glucose or glycated hemoglobin percentage (Hb1Ac) was measured in 12 of the 43 cases; while antidiabetic medication was found in 14 of the cases (only two of the cases had both glucose measurements and medication). With the increasing prevalence of DM, a possibility of pilot incapacitation due to DM or complications of DM should be actively studied, even if no anamnestic information of DM was available. While PM hypoglycemia is difficult to assess, we propose a systematic investigation based on measurement of glucose, Hb1Ac%, and ketone bodies, and documentation of atherosclerotic lesions in major arteries to identify or rule out DM as a cause of pilot incapacitation.

Subjective and objective measures of function and return to work: an observational study with a clinical psychiatric cohort.

PURPOSE: To evaluate the association between two measurement tools (Social and Occupational Functioning Assessment Scale, SOFAS and Sheehan Disability Scale, SDS), returning to work (RTW) and their inter-correlation. METHODS: 132 psychiatric patients referred to assessment of work ability participated. The association between SOFAS and SDS Work to RTW were assessed by logistic regression. Inter-correlations between SOFAS and SDS were assessed with the Spearman's rho correlation coefficient. RESULTS: SOFAS and SDS Work scores were associated with a 1-year RTW and SOFAS and SDS were inter-correlated. CONCLUSIONS: When assigning the ability to work, both subjective and objective measures of function predict RTW.

TSLP expression: analysis with a ZsGreen TSLP reporter mouse.

Thymic stromal lymphopoietin (TSLP) is a type I cytokine that plays a central role in induction of allergic inflammatory responses. Its principal targets have been reported to be dendritic cells and/or CD4 T cells; epithelial cells are a principal source. We report in this study the development of a reporter mouse (TSLP-ZsG) in which a ZsGreen (ZsG)-encoding construct has been inserted by recombineering into a bacterial artificial chromosome immediately at the translation initiating ATG of TSLP. The expression of ZsG by mice transgenic for the recombinant BAC appears to be a faithful surrogate for TSLP expression, particularly in keratinocytes and medullary thymic epithelial cells. Limited ZsG and TSLP mRNA was observed in bone marrow-derived mast cells, basophils, and dendritic cells. Using the TSLP-ZsG reporter mouse, we show that TNF-α and IL-4/IL-13 are potent inducers of TSLP expression by keratinocytes and that local activation of Th2 and Th1 cells induces keratinocyte TSLP expression. We suggest that the capacity of TSLP to both induce Th2 differentiation and to be induced by activated Th2 cells raises the possibility that TSLP may be involved in a positive feedback loop to enhance allergic inflammatory conditions.

Proprotein convertase FURIN constrains Th2 differentiation and is critical for host resistance against Toxoplasma gondii.

The proprotein convertase subtilisin/kexin enzymes proteolytically convert immature proproteins into bioactive molecules, and thereby they serve as key regulators of cellular homeostasis. The archetype proprotein convertase subtilisin/kexin, FURIN, is a direct target gene of the IL-12/STAT4 pathway and it is upregulated in Th1 cells. We have previously demonstrated that FURIN expression in T cells critically regulates the maintenance of peripheral immune tolerance and the functional maturation of pro-TGF-ß1 in vivo, but FURIN's role in cell-mediated immunity and Th polarization has remained elusive. In this article, we show that T cell-expressed FURIN is essential for host resistance against a prototypic Th1 pathogen, Toxoplasma gondii, and for the generation of pathogen-specific Th1 lymphocytes, including Th1-IL-10 cells. FURIN-deficient Th cells instead show elevated expression of IL-4R subunit α on cell surface, sensitized IL-4/STAT6 signaling, and a propensity to polarize toward the Th2 phenotype. By exploring FURIN-interacting proteins in Jurkat T cells with Strep-Tag purification and mass spectrometry, we further identify an association with a cytoskeleton modifying Ras-related C3 botulinum toxin substrate/dedicator of cytokinesis 2 protein complex and unravel that FURIN promotes F-actin polymerization, which has previously been shown to downregulate IL-4R subunit α cell surface expression and promote Th1 responses. In conclusion, our results demonstrate that in addition to peripheral immune tolerance, T cell-expressed FURIN is also a central regulator of cell-mediated immunity and Th1/2 cell balance.

[Innate lymphoid cells - a new group of immune cells]. / Luontaiset Iymfosyytit - uusi immuunisoluryhmä.

A new group of immune cells, innate lymphoid cells, i.e. ILC cells has recently been identified in the territory between the cells of innate and acquired immunity. While the understanding of their functioning and grouping still remains incomplete, their importance in defending the interfaces of the body seems clear. The central role of ILC cells is to sense danger signals in the body and modify immune responses on the basis of this information. In addition to understanding of the defense response, future research. on ILC cells is expected to provide information about the mechanisms of autoimmunity and allergic inflammation as well as disorders of immunity associated with cancer and obesity.

The activity of JAK-STAT pathways in rheumatoid arthritis: constitutive activation of STAT3 correlates with interleukin 6 levels.

OBJECTIVE: Many cytokines involved in RA activate the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathways. Therapeutic drugs that inhibit these pathways are being developed for RA. To investigate disease-related alterations in the activity of JAK-STAT pathways in RA, we studied the expression and activation of STAT1 and STAT3 in unstimulated and cytokine-stimulated cells and determined the levels of circulating cytokines. METHODS: The expression of STAT1 and STAT3 mRNA in peripheral blood (PB) and SF T cells and monocytes was studied in RA patients and healthy volunteers by RT-PCR. Basal and cytokine (IFN-γ, IL-6, IL-10)-induced STAT phosphorylation was analysed in PB T cells and monocytes using multicolour flow cytometric analysis. RESULTS: STAT3 mRNA levels were up-regulated in both PB and SF T cells and monocytes from RA patients. STAT1 expression was elevated in SF monocytes. The levels of phospho-STAT3 in resting PB T cells and monocytes were significantly higher in patients with RA than in healthy volunteers. IL-6 levels were elevated in RA plasma and correlated with the level of STAT3 phosphorylation in CD4(+) T cells and monocytes. IL-6-mediated STAT3 activation was deregulated in T cells from RA patients. IL-6-induced phosphorylation of STAT3 was decreased in CD4(+) T cells from patients with high plasma IL-6 levels and constitutive STAT3 phosphorylation. CONCLUSION: The results suggest that IL-6 induces hyperactivation of STAT3 in circulating immune cells in active RA, and this subsequently desensitizes the IL-6 response in T cells.

Cytokine-induced cytokine production by conventional and innate lymphoid cells.

Innate immune and differentiated T cells produce signature cytokines in response to cytokine stimulation. Optimal production requires stimulation by an NF-κB inducer, most commonly an interleukin (IL)-1 family member, and a STAT activator. Usually, there is linkage between the IL-1 family member, the activated STAT and the cytokines produced: IFNγ producers respond to the IL-1 family member, IL-18 and IL-12, a STAT4 activator; IL-13 producers respond to IL-33 (although for ILC2 cells this may be replaced by IL-25) and STAT5 activators; for cells producing IL-17A or IL-22, the combination is IL-1 and a STAT3 inducer. Cytokine-induced cytokine production may have broad significance in orchestrating innate responses to distinct infectious agents and in maintaining inflammatory responses after elimination of the inciting antigen.

Redirecting cell-type specific cytokine responses with engineered interleukin-4 superkines.

Cytokines dimerize their receptors, with the binding of the 'second chain' triggering signaling. In the interleukin (IL)-4 and IL-13 system, different cell types express varying numbers of alternative second receptor chains (γc or IL-13Rα1), forming functionally distinct type I or type II complexes. We manipulated the affinity and specificity of second chain recruitment by human IL-4. A type I receptor-selective IL-4 'superkine' with 3,700-fold higher affinity for γc was three- to ten-fold more potent than wild-type IL-4. Conversely, a variant with high affinity for IL-13Rα1 more potently activated cells expressing the type II receptor and induced differentiation of dendritic cells from monocytes, implicating the type II receptor in this process. Superkines showed signaling advantages on cells with lower second chain numbers. Comparative transcriptional analysis reveals that the superkines induce largely redundant gene expression profiles. Variable second chain numbers can be exploited to redirect cytokines toward distinct cell subsets and elicit new actions, potentially improving the selectivity of cytokine therapy.

Efficient cytokine-induced IL-13 production by mast cells requires both IL-33 and IL-3.

BACKGROUND: IL-13 is a critical effector cytokine for allergic inflammation. It is produced by several cell types, including mast cells, basophils, and TH2 cells. In mast cells and basophils its induction can be stimulated by cross-linkage of immunoglobulin receptors or cytokines. The IL-1 family members IL-33 and IL-18 have been linked to induction of IL-13 production by mast cells and basophils. In CD4 TH2 cells IL-33-mediated production of IL-13 requires simultaneous signal transducer and activator of transcription (STAT) 5 activation. OBJECTIVE: Here we have addressed whether cytokine-induced IL-13 production in mast cells and basophils follows the same logic as in TH2 cells: requirement of 2 separate signals. METHODS: By generating a bacterial artificial chromosome (BAC) transgenic IL-13 reporter mouse, we measured IL-13 production in mast cells and basophils. RESULTS: In mast cells harvested from peritoneal cavities, 2 cytokine signals are required for IL-13 production: IL-33 and IL-3. In bone marrow mast cells IL-13 production requires IL-33, but the requirement for a STAT5 inducer is difficult to evaluate because these cells require the continuous presence of IL-3 (a STAT5 activator) for survival. Poorer STAT5 inducers in culture (IL-4 or stem cell factor) result in less IL-13 production on IL-33 challenge, but the addition of exogenous IL-3 enhances IL-13 production. This implies that bone marrow-derived mast cells, like peritoneal mast cells and TH2 cells, require stimulation both by an IL-1 family member and a STAT5 inducer to secrete IL-13. Basophils follow the same rule; splenic basophils produce IL-13 in response to IL-18 or IL-33 plus IL-3. CONCLUSION: Optimal IL-13 production from mast cells and basophils requires 2 cytokine signals.

S-layer protein mediates the stimulatory effect of Lactobacillus helveticus MIMLh5 on innate immunity.

The ability to positively affect host health through the modulation of the immune response is a feature of increasing importance in measuring the probiotic potential of a bacterial strain. However, the identities of the bacterial cell components involved in cross talk with immune cells remain elusive. In this study, we characterized the dairy strain Lactobacillus helveticus MIMLh5 and its surface-layer protein (SlpA) using in vitro and ex vivo analyses. We found that MIMLh5 and SlpA exert anti-inflammatory effects by reducing the activation of NF-κB on the intestinal epithelial Caco-2 cell line. On the contrary, MIMLh5 and SlpA act as stimulators of the innate immune system by triggering the expression of proinflammatory factors tumor necrosis factor alpha and COX-2 in the human macrophage cell line U937 via recognition through Toll-like receptor 2. In the same experiments, SlpA protein did not affect the expression of the anti-inflammatory cytokine interleukin-10. A similar response was observed following stimulation of macrophages isolated from mouse bone marrow or the peritoneal cavity. These results suggest that SlpA plays a major role in mediating bacterial immune-stimulating activity, which could help to induce the host's defenses against and responses toward infections. This study supports the concept that the viability of bacterial cells is not always essential to exert immunomodulatory effects, thus permitting the development of safer therapies for the treatment of specific diseases according to a paraprobiotic intervention.