NRF2 Plays a Crucial Role in the Tolerogenic Effect of Ethyl Pyruvate on Dendritic Cells.

Ethyl pyruvate (EP) is a redox-active compound that has been previously shown to be effective in restraining immune hyperactivity in animal models of various autoimmune and chronic inflammatory diseases. Importantly, EP has also been proven to have a potent tolerogenic effect on dendritic cells (DCs). Here, the influence of EP on the signaling pathways in DCs relevant for their tolerogenicity, including anti-inflammatory NRF2 and pro-inflammatory NF-κB, was explored. Specifically, the effects of EP on DCs obtained by GM-CSF-directed differentiation of murine bone marrow precursor cells and matured under the influence of lipopolysaccharide (LPS) were examined via immunocytochemistry and RT-PCR. EP counteracted LPS-imposed morphological changes and down-regulated the LPS-induced expression of pro-inflammatory mediators in DCs. While it reduced the activation of NF-κB, EP potentiated NRF2 and downstream antioxidative molecules, thus implying the regulation of NRF2 signaling pathways as the major reason for the tolerizing effects of EP on DCs.

Ethyl pyruvate ameliorates acute respiratory distress syndrome in mice.

Acute respiratory distress syndrome (ARDS) became a focus of intensive research due to its death toll during the Covid-19 pandemic. An uncontrolled and excessive inflammatory response mediated by proinflammatory molecules such as high mobility group box protein 1 (HMGB1), IL-6, and TNF mounts as a response to infection. In this study, ethyl pyruvate (EP), a known inhibitor of HMGB1, was tested in the model of murine ARDS induced in C57BL/6 mice by intranasal administration of polyinosinic:polycytidylic acid (poly(I:C)). Intraperitoneal administration of EP ameliorated the ARDS-related histopathological changes in the lungs of poly(I:C)-induced ARDS and decreased numbers of immune cells in the lungs, broncho-alveolar lavage fluid and draining lymph nodes (DLN). Specifically, fewer CD8+ T cells and less activated CD4+ T cells were observed in DLN. Consequently, the lungs of EP-treated animals had fewer damage-inflicting CD8+ cells and macrophages. Additionally, the expression and production of proinflammatory cytokines, IL-17, IFN-γ and IL-6 were downregulated in the lungs. The expression of chemokine CCL5 which recruits immune cells into the lungs was also reduced. Finally, EP downregulated the expression of HMGB1 in the lungs. Our results imply that EP should be further evaluated as a potential candidate for ARDS therapy.

Brain inflammation in experimental autoimmune encephalomyelitis induced in Dark Agouti rats with spinal cord homogenate.

We have recently characterized experimental autoimmune encephalomyelitis (EAE) induced in DA rats with spinal cord homogenate without complete Freund's adjuvant (CFA). The main advantage of this multiple sclerosis model is the lack of CFA-related confounding effects which represent the major obstacles in translating findings from EAE to multiple sclerosis. Here, antigen specificity of the cellular and humoral immune response directed against the central nervous system was explored. The reactivity of T and B cells to myelin basic protein, myelin oligodendrocyte glycoprotein, and ß-synuclein was detected. Having in mind that reactivity against ß-synuclein was previously associated with autoimmunity against the brain, the infiltration of immune cells into different brain compartments, i.e. pons, cerebellum, hippocampus, and cortex was determined. T cell infiltration was observed in all structures examined. This finding stimulated investigation of the effects of immunization on DA rat behavior using the elevated plus maze and the open field test. Rats recovered from EAE displayed increased anxiety-like behavior. These data support CFA-free EAE in DA rats as a useful model for multiple sclerosis research.

Increased regulatory activity of intestinal innate lymphoid cells type 3 (ILC3) prevents experimental autoimmune encephalomyelitis severity.

Experimental autoimmune encephalomyelitis (EAE) induced in inbred rodents, i.e., genetically identical animals kept under identical environmental conditions, shows variable clinical outcomes. We investigated such variations of EAE in Dark Agouti rats immunized with spinal cord homogenate and identified four groups: lethal, severe, moderate, and mild, at day 28 post immunization. Higher numbers of CD4+ T cells, helper T cells type 1 (Th1) and 17 (Th17) in particular, were detected in the spinal cord of the severe group in comparison with the moderate group. In addition, increased proportion of Th1 and Th17 cells, and heightened levels of interferon (IFN)-γ and interleukin (IL)-6 were detected in the small intestine lamina propria of the severe group. A selective agonist of free fatty acid receptor type 2 (Ffar2) applied orally in the inductive phase of EAE shifted the distribution of the disease outcomes towards milder forms. This effect was paralleled with potentiation of intestinal innate lymphoid cells type 3 (ILC3) regulatory properties, and diminished Th1 and Th17 cell response in the lymph nodes draining the site of immunization. Our results suggest that different clinical outcomes in DA rats are under determinative influence of intestinal ILC3 activity during the inductive phase of EAE.

ILC3: a case of conflicted identity.

Innate lymphoid cells type 3 (ILC3s) are the first line sentinels at the mucous tissues, where they contribute to the homeostatic immune response in a major way. Also, they have been increasingly appreciated as important modulators of chronic inflammatory and autoimmune responses, both locally and systemically. The proper identification of ILC3 is of utmost importance for meaningful studies on their role in immunity. Flow cytometry is the method of choice for the detection and characterization of ILC3. However, the analysis of ILC3-related papers shows inconsistency in ILC3 phenotypic definition, as different inclusion and exclusion markers are used for their identification. Here, we present these discrepancies in the phenotypic characterization of human and mouse ILC3s. We discuss the pros and cons of using various markers for ILC3 identification. Furthermore, we consider the possibilities for the efficient isolation and propagation of ILC3 from different organs and tissues for in-vitro and in-vivo studies. This paper calls upon uniformity in ILC3 definition, isolation, and propagation for the increased possibility of confluent interpretation of ILC3's role in immunity.

Development of Type 1 Diabetes in Mice Is Associated with a Decrease in IL-2-Producing ILC3 and FoxP3+ Treg in the Small Intestine.

Recent data indicate the link between the number and function of T regulatory cells (Treg) in the gut immune tissue and initiation and development of autoimmunity associated with type 1 diabetes (T1D). Since type 3 innate lymphoid cells (ILC3) in the small intestine are essential for maintaining FoxP3+ Treg and there are no data about the possible role of ILC3 in T1D pathogenesis, the aim of this study was to explore ILC3-Treg link during the development of T1D. Mature diabetic NOD mice had lower frequencies of IL-2-producing ILC3 and Treg in small intestine lamina propria (SILP) compared to prediabetic NOD mice. Similarly, in multiple low doses of streptozotocin (MLDS)-induced T1D in C57BL/6 mice, hyperglycemic mice exhibited lower numbers of ILC3, IL-2+ ILC3 and Treg in SILP compared to healthy controls. To boost T1D severity, mice were treated with broad-spectrum antibiotics (ABX) for 14 days prior to T1D induction by MLDS. The higher incidence of T1D in ABX-treated mice was associated with significantly lower frequencies of IL-2+ ILC3 and FoxP3+ Treg in SILP compared with mice without ABX treatment. The obtained findings show that the lower proportions of IL-2-expressing ILC3 and FoxP3+ Treg in SILP coincided with diabetes progression and severity.

Phenethyl Ester of Gallic Acid Ameliorates Experimental Autoimmune Encephalomyelitis.

Gallic acid is a phenolic acid present in various plants, nuts, and fruits. It is well known for its anti-oxidative and anti-inflammatory properties. The phenethyl ester of gallic acid (PEGA) was synthesized with the aim of increasing the bioavailability of gallic acid, and thus its pharmacological potential. Here, the effects of PEGA on encephalitogenic cells were examined, and PEGA was found to modulate the inflammatory activities of T cells and macrophages/microglia. Specifically, PEGA reduced the release of interleukin (IL)-17 and interferon (IFN)-γ from T cells, as well as NO, and IL-6 from macrophages/microglia. Importantly, PEGA ameliorated experimental autoimmune encephalomyelitis, an animal model of chronic inflammatory disease of the central nervous system (CNS)-multiple sclerosis. Thus, PEGA is a potent anti-inflammatory compound with a perspective to be further explored in the context of CNS autoimmunity and other chronic inflammatory disorders.

Acetylsalicylic-acid (ASA) regulation of osteo/odontogenic differentiation and proliferation of human dental pulp stem cells (DPSCs) in vitro.

OBJECTIVE: The study aimed to investigate acetylsalicylic acid (ASA) effects on osteo/odontogenic differentiation and proliferation of dental pulp stem cells (DPSCs) in vitro and the potential involvement of adenosine monophosphate-activated protein kinase (AMPK) pathway in these processes. DESIGN: DPSCs were isolated from third molars pulp tissues of five patients and grown in osteogenic medium alone or supplemented with ASA. Expression of DPSCs markers was tested by flow-cytometry. Cytotoxicity of ASA at concentrations of 10, 50 and 100 µg/ml was tested by MTT and NR assays. Osteo/odontogenic differentiation was analyzed via alizarin red staining and ALP activity. Quantitative PCR (qPCR) was used for osteo/odontogenic markers' (DSPP, BMP2, BMP4, BSP, OCN and RUNX2) and c-Myc expression analysis. AMPK inhibition of ASA-induced osteo/odontogenesis was tested by qPCR of selected markers (DSPP, OCN and RUNX2). RESULTS: Cytotoxicity assays showed that only the highest ASA dose decreased cell viability (89.1 %). The smallest concentration of ASA applied on DPSCs resulted in a remarkable enhancement of osteo/odontogenic differentiation, as judged by increased mineralized nodules' formation, ALP activity and gene expression of analyzed markers (increase between 2 and 30 folds), compared to untreated cells. ASA also increased DPSCs proliferation. Interestingly, AMPK inhibition per se upregulated DSPP, OCN and RUNX2; the gene upregulation was higher when ASA treatment was also included. c-Myc expression level decreased in cultures treated with ASA, indicating undergoing differentiation processes. CONCLUSIONS: Low concentrations of ASA (corresponding to the standard use in cardiovascular patients), were shown to stimulate osteo/odontogenic differentiation of dental pulp stem cells.

Phenethyl ester of rosmarinic acid ameliorates experimental autoimmune encephalomyelitis.

Rosmarinic acid is a polyphenolic compound, abundantly present in herbs of the Lamiaceae family. The aim of the study was to evaluate the immunomodulatory properties of a recently developed phenethyl ester derivative of rosmarinic acid (PERA), with enhanced ability of diffusion through biological membranes, in an animal model of the central nervous system (CNS) autoimmunity. To this end, experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis was used. Daily subcutaneous administration of PERA (30 mg/kg) from day 7 to day 22 after immunization successfully ameliorated EAE induced in Dark Agouti rats, shortening the disease duration and reducing maximal, cumulative and mean clinical score. PERA efficiently reduced production of major encephalitogenic cytokines, interferon (IFN)-γ and interleukin (IL)-17, in immune cells from the CNS or the lymph nodes draining the site of immunization of EAE rats, as well as in CD4+ T cells purified from the lymph nodes. Also, PERA inhibited NO production in the CNS and the lymph nodes, as well as in macrophages and microglial cells. Finally, microglial ability to produce pro-inflammatory cytokines IL-6, and tumor necrosis factor (TNF) were also reduced by PERA. Our results clearly imply that PERA possesses anti-encephalitogenic properties. Thus, further studies on the relevance of the observed effects for the therapy of multiple sclerosis are warranted.

ILC3, a Central Innate Immune Component of the Gut-Brain Axis in Multiple Sclerosis.

Gut immune cells have been increasingly appreciated as important players in the central nervous system (CNS) autoimmunity in animal models of multiple sclerosis (MS). Among the gut immune cells, innate lymphoid cell type 3 (ILC3) is of special interest in MS research, as they represent the innate cell counterpart of the major pathogenic cell population in MS, i.e. T helper (Th)17 cells. Importantly, these cells have been shown to stimulate regulatory T cells (Treg) and to counteract pathogenic Th17 cells in animal models of autoimmune diseases. Besides, they are also well known for their ability to stabilize the intestinal barrier and to shape the immune response to the gut microbiota. Thus, proper maintenance of the intestinal barrier and the establishment of the regulatory milieu in the gut performed by ILC3 may prevent activation of CNS antigen-specific Th17 cells by the molecular mimicry. Recent findings on the role of ILC3 in the gut-CNS axis and their relevance for MS pathogenesis will be discussed in this paper. Possibilities of ILC3 functional modulation for the benefit of MS patients will be addressed, as well.

Antimicrobial and Immunomodulating Activities of Two Endemic Nepeta Species and Their Major Iridoids Isolated from Natural Sources.

Two Balkan Peninsula endemics, Nepeta rtanjensis and N. argolica subsp. argolica, both characterized by specialized metabolite profiles predominated by iridoids and phenolics, are differentiated according to the stereochemistry of major iridoid aglycone nepetalactone (NL). For the first time, the present study provides a comparative analysis of antimicrobial and immunomodulating activities of the two Nepeta species and their major iridoids isolated from natural sources-cis,trans-NL, trans,cis-NL, and 1,5,9-epideoxyloganic acid (1,5,9-eDLA), as well as of phenolic acid rosmarinic acid (RA). Methanol extracts and pure iridoids displayed excellent antimicrobial activity against eight strains of bacteria and seven strains of fungi. They were especially potent against food-borne pathogens such as L. monocytogenes, E. coli, S. aureus, Penicillium sp., and Aspergillus sp. Targeted iridoids were efficient agents in preventing biofilm formation of resistant P. aeruginosa strain, and they displayed additive antimicrobial interaction. Iridoids are, to a great extent, responsible for the prominent antimicrobial activities of the two Nepeta species, although are probably minor contributors to the moderate immunomodulatory effects. The analyzed iridoids and RA, individually or in mixtures, have the potential to be used in the pharmaceutical industry as potent antimicrobials, and in the food industry to increase the shelf life and safety of food products.

Complete Freund's adjuvant-free experimental autoimmune encephalomyelitis in Dark Agouti rats is a valuable tool for multiple sclerosis studies.

Experimental autoimmune encephalomyelitis (EAE) is classically induced with complete Freund's adjuvant (CFA). The immune response against CFA has a confounding influence on the translational capacity of EAE as a multiple sclerosis model. Here, we compare clinical, cellular and molecular properties between syngeneic spinal cord homogenate (SCH)- and SCH + CFA-immunized Dark Agouti rats. EAE signs were observed earlier and the cumulative clinical score was higher without CFA. Also, a higher number of immune cells infiltrates in the spinal cords was noticed at the peak of EAE without CFA. High spinal cord abundance of CD8+CD11bc+MHC class II+ cells was detected in SCH-immunized rats. Myelin basic protein -specific response can be elicited in the cells from the lymph nodes draining the site of SCH immunization. This CFA-free EAE is a reliable multiple sclerosis model.

Redox Regulation of Tolerogenic Dendritic Cells and Regulatory T Cells in the Pathogenesis and Therapy of Autoimmunity.

Significance: Autoimmune diseases are progressively affecting westernized societies, as the proportion of individuals suffering from autoimmunity is steadily increasing over the past decades. Understanding the role of reactive oxygen species (ROS) in modulation of the immune response in the pathogenesis of autoimmune disorders is of utmost importance. The focus of this review is the regulation of ROS production within tolerogenic dendritic cells (tolDCs) and regulatory T (Treg) cells that have the essential role in the prevention of autoimmune diseases and significant potency in their therapy. Recent Advances: It is now clear that ROS are extremely important for the proper function of both DC and T cells. Antigen processing/presentation and the ability of DC to activate T cells depend upon the ROS availability. Treg differentiation, suppressive function, and stability are profoundly influenced by ROS presence. Critical Issues: Although a plethora of results on the relation between ROS and immune cells exist, it remains unclear whether ROS modulation is a productive way for skewing T cells and DCs toward a tolerogenic phenotype. Also, the possibility of ROS modulation for enhancement of regulatory properties of DC and Treg during their preparation for use in cellular therapy has to be clarified. Future Directions: Studies of DC and T cell redox regulation should allow for the improvement of the therapy of autoimmune diseases. This could be achieved through the direct therapeutic application of ROS modulators in autoimmunity, or indirectly through ROS-dependent enhancement of tolDC and Treg preparation for cell-based immunotherapy. Antioxid. Redox Signal. 34, 364-382.

Upregulation of Tolerogenic Pathways by the Hydrogen Sulfide Donor GYY4137 and Impaired Expression of H2S-Producing Enzymes in Multiple Sclerosis.

The aim of this study was to examine the in vitro effects of the slow-releasing H2S donor GYY4137 on the immune cells involved in the pathogenesis of the central nervous system (CNS) autoimmune disease, multiple sclerosis (MS). GYY4137 specifically potentiated TGF-ß expression and production in dendritic cells and significantly reduced IFN-γ and IL-17 production in the lymph node and spinal cord T cells obtained from mice immunized with CNS antigens. Both the proportion of FoxP3+ regulatory CD4+ T cells in the lymph node cells, and the percentage of IL-17+ CD4+ T cells in the spinal cord cells were reduced upon culturing with GYY4137. Interestingly, the peripheral blood mononuclear cells obtained from the MS patients had a lower expression of the H2S-producing enzyme, 3-mercaptopyruvate-sulfurtransferase (MPST), in comparison to those obtained from healthy donors. A significant inverse correlation between the expression of MPST and several pro-inflammatory factors was also observed. Further studies on the relevance of the observed results for the pathogenesis and therapy of MS are warranted.

Ethyl Pyruvate Induces Tolerogenic Dendritic Cells.

Dendritic cells (DC) are professional antigen presenting cells that have a key role in shaping the immune response. Tolerogenic DC (tolDC) have immuno-regulatory properties and they are a promising prospective therapy for multiple sclerosis and other autoimmune diseases. Ethyl pyruvate (EP) is a redox analog of dimethyl fumarate (Tecfidera), a drug for multiple sclerosis treatment. We have recently shown that EP ameliorates experimental autoimmune encephalomyelitis, a multiple sclerosis murine model. Here, we expanded our study to its tolerogenic effects on DC. Phenotypic analysis has shown that DC obtained from mice or humans reduce expression of molecules required for T cell activation such as CD86, CD83, and HLA-DR under the influence of EP, while CD11c expression and viability of DC are not affected. Furthermore, EP-treated DC restrain proliferation and modulate cytokine production of allogeneic lymphocytes. These results demonstrate that EP has the ability to direct DC toward tolDC.

Comparison of dendritic cells obtained from autoimmunty-prone and resistant rats.

Dendritic cells (DC) are responsible for the initiation and shaping of the adaptive immune response and are in the focus of autoimmunity research. We were interested in comparison of DC obtained from autoimmunity-prone Dark Agouti (DA) rats and autoimmunity-resistant Albino Oxford (AO) rats. DC were generated from bone marrow precursors and matured (mDC) by lipopolysaccharide. Tolerogenic DC (tolDC) obtained by vitamin D3 treatment were studied in parallel. Profile of cytokine production was different in AO and DA mDC and tolDC. Expression of MHC class II molecules and CD86 were higher in DA DC, while vitamin D3 reduced their expression in dendritic cells of both strains. Allogeneic proliferation of CD4+ T cells was reduced by AO tolDC, but not with DA tolDC in comparison to respective mDC. Finally, expression of various genes identified as differentially expressed in human mDC and tolDC was also analyzed in AO and DA DC. Again, AO and DA DC differed in the expression of the analyzed genes. To conclude, AO and DA DC differ in production of cytokines, expression of antigen presentation-related molecules and in regulation of CD4+ T proliferation. The difference is valuable for understanding the divergence of the strains in their susceptibility to autoimmunity.

Oral neonatal antibiotic treatment perturbs gut microbiota and aggravates central nervous system autoimmunity in Dark Agouti rats.

Gut microbiota dysbiosis has been considered the essential element in the pathogenesis of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). Antibiotics were administered orally to Dark Agouti (DA) rats early in their life with the aim of perturbing gut microbiota and investigating the effects of such intervention on the course of EAE. As a result, the diversity of the gut microbiota was reduced under the influence of antibiotics. Mainly, Firmicutes and Actinobacteria were replaced by Proteobacteria and Bacteroidetes, while decreased proportions of Clostridia and Bacilli classes were accompanied by an increase in Gamma-Proteobacteria in antibiotic-treated animals. Interestingly, a notable decrease in the Helicobacteraceae, Spirochaetaceae and Turicibacteriaceae was scored in antibiotic-treated groups. Also, levels of short chain fatty acids were reduced in the faeces of antibiotic-treated rats. Consequently, aggravation of EAE, paralleled with stronger immune response in lymph nodes draining the site of immunization, and increased inflammation within the CNS, were observed in antibiotic-treated DA rats. Thus, the alteration of gut microbiota leads to an escalation of CNS-directed autoimmunity in DA rats. The results of this study indicate that antibiotic use in early life may have subsequent unfavourable effects on the regulation of the immune system.

Gut Microbiota Confers Resistance of Albino Oxford Rats to the Induction of Experimental Autoimmune Encephalomyelitis.

Albino Oxford (AO) rats are extremely resistant to induction of experimental autoimmune encephalomyelitis (EAE). EAE is an animal model of multiple sclerosis, a chronic inflammatory disease of the central nervous system (CNS), with established autoimmune pathogenesis. The autoimmune response against the antigens of the CNS is initiated in the peripheral lymphoid tissues after immunization of AO rats with CNS antigens. Subsequently, limited infiltration of the CNS occurs, yet without clinical sequels. It has recently become increasingly appreciated that gut-associated lymphoid tissues (GALT) and gut microbiota play an important role in regulation and propagation of encephalitogenic immune response. Therefore, modulation of AO gut microbiota by antibiotics was performed in this study. The treatment altered composition of gut microbiota in AO rats and led to a reduction in the proportion of regulatory T cells in Peyer's patches, mesenteric lymph nodes, and in lymph nodes draining the site of immunization. Upregulation of interferon-γ and interleukin (IL)-17 production was observed in the draining lymph nodes. The treatment led to clinically manifested EAE in AO rats with more numerous infiltrates and higher production of IL-17 observed in the CNS. Importantly, transfer of AO gut microbiota into EAE-prone Dark Agouti rats ameliorated the disease. These results clearly imply that gut microbiota is an important factor in AO rat resistance to EAE and that gut microbiota transfer is an efficacious way to treat CNS autoimmunity. These findings also support the idea that gut microbiota modulation has a potential as a future treatment of multiple sclerosis.

Anti-encephalitogenic effects of ethyl pyruvate are reflected in the central nervous system and the gut.

Ethyl pyruvate is a redox analogue of dimethyl fumarate (Tecfidera), a drug for multiple sclerosis treatment. We have recently shown that ethyl pyruvate ameliorates experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. It affects encephalitogenic T cells and macrophages in vitro, as well as in lymph nodes draining the site of encephalitogenic immunization and within the central nervous system (CNS). Here, in vivo effects of ethyl pyruvate on EAE are thoroughly investigated in the CNS and within the gut associated lymphoid tissue. Ethyl pyruvate reduced infiltrates within the CNS and number of activated macrophages/microglia (ED1+/Iba1+) and proliferating astrocytes (GFAP+). Furthermore, it reduced expression of HMGB1 in activated macrophages/microglia. It also reduced number of activated T cells and antigen-presenting cells and expression of Th1/Th17-related molecules in mesenteric lymph nodes and Peyer's patches. These results contribute to our understanding of anti-encephalitogenic effects of ethyl pyruvate as they provide evidence of its effects within the CNS and imply that these effects are related to reduction of inflammatory immune response in gut associated lymphoid tissue.

Strain-specific helper T cell profile in the gut-associated lymphoid tissue.

C57BL/6, BALB/c and NOD mice are among the most frequently used strains in autoimmunity research. NOD mice spontaneously develop type 1 diabetes (T1D) and they are prone to induction of experimental autoimmune encephalomyelitis (EAE). Both diseases can be routinely induced in C57BL/6 mice, but not in BALB/c mice. Also, C57BL/6 mice are generally considered T helper (Th)1-biased and BALB/c Th2-biased mice. Having in mind increasingly appreciated role of gut associated lymphoid tissue (GALT) cells in autoimmunity, especially in relation to gut Th17 and regulatory T (Treg) cells, our aim was to determine if there are differences in proportion of CD4+ T cell populations in mesenteric lymph nodes and Peyer's patches of these mouse strains. Lower proportion of Treg was observed in NOD PP, Th2 cells dominated in BALB/c mice in mesenteric lymph nodes (MLN) and Peyer's patches (PP), while Th1 cells prevailed in C57BL/6 MLN. Intradermal immunization of mice with complete Freund's adjuvant resulted in significant difference in Th cell distribution in GALT of NOD mice. Differences were less pronounced in C57BL/6 mice, while GALT of BALB/c mice was almost unresponsive to the immunization. The observed strain- and tissue-dependent changes in Treg proportion after the immunization was probably a consequence of different CCR2 or CCR6-related migration patterns and/or in situ Treg proliferation. In conclusion, NOD, a highly autoimmunity-prone mouse strain, exhibits more profound GALT-related immune response upon immunization compared to the strains that are less prone to autoimmunity.