PTPN22 Allele Research Articles

Improving immunity against chronic virus infection using an autoimmunity associated Ptpn22 allele.

Abstract Dysfunctional dendritic cells (DC) lead to inadequate T cell activation causing chronic virus infection. Enhancing both DC and T cell function can prevent chronic virus infection. An approach to enhance immune function is to harness the immune-activating phenotype driven by the autoimmunity-associated allele of PTPN22, which is expressed in all immune cells. We previously found that mice expressing the Ptpn22 autoimmunity-associated allele (Ptpn22-R619W) successfully clear Lymphocytic choriomeningitis virus clone 13 (LCMV-cl13) unlike wildtype (WT) mice. This correlates with a more immunostimulatory DC phenotype and enhanced T cell function. However, the mechanism Ptpn22-R619W enhances DC and T cell function remains unclear. Using our CRISPR/cas9 generated Ptpn22-R619W mice, we addressed the hypothesis that Ptpn22-R619W increases DC immunostimulatory proteins which increases anti-viral T cell activation during virus infection. Post infection, Ptpn22-R619W DCs have reduced infection, increased CD86, and decreased PD-L1 expression both in vivo and ex vivo. Additionally, Ptpn22-R619W DCs have a differential gene expression profile. Also, Ptpn22-R619W mice have enhanced CD8 T cell function against the LCMV-cl13 minor epitope, GP276, but not the major epitope. Lastly, co-culture experiments demonstrate that Ptpn22-R619W in both DC and T cells is necessary to enhance T cell function. These results show how Ptpn22-R619W prevents DC and T cell dysfunction during virus infection.

The Autoimmunity-Associated Minor Allele of PTPN22 Enhances Antiviral Immunity During Coronavirus Infection

Abstract The deadly consequences of viral infection were clearly demonstrated by the COVID-19 pandemic. Therefore, identifying new therapeutic targets to enhance our antiviral immunity and combat virus infection is essential, such as the immune-regulatory gene PTPN22. 5-15% of North Americans express a PTPN22 alternative allele which is linked with multiple autoimmune diseases. However, there is a significant research gap regarding the role of PTPN22 and its common allele during viral infection. To address this, we used CRISPR/Cas9 generated Ptpn22 knockout (PEP-null) and Ptpn22 minor allele expressing (PEP-619WW) mice and infected them with the common murine model of coronavirus, Mouse Hepatitis Virus (MHV) A59. We hypothesize that PEP-null and PEP-619WW mice have enhanced antiviral immunity during coronavirus infection. Following MHV A59 infection, PEP-null and PEP-619WW mice have reduced weight loss and increased survival over WT mice. Additionally, PEP-null and PEP-619WW mice have enhanced innate immunity, such as increased Natural Killer (NK) cell numbers. Furthermore, we show that PEP-null and PEP-619WW innate immune cells offer enhanced protection during MHV A59 infection, but lymphocytes are necessary for survival. These results demonstrate that PEP-null and PEP-619WW are beneficial during coronavirus infection. This research sets the precedent to interrogate the role of Ptpn22 in other RNA virus infections and as a novel therapeutic target to enhance antiviral immunity.

Autoimmunity-associated allele of tyrosine phosphatase gene PTPN22 enhances anti-viral immunity.

The 1858C>T allele of the tyrosine phosphatase PTPN22 is present in 5-10% of the North American population and is strongly associated with numerous autoimmune diseases. Although research has been done to define how this allele potentiates autoimmunity, the influence PTPN22 and its pro-autoimmune allele has in anti-viral immunity remains poorly defined. Here, we use single cell RNA-sequencing and functional studies to interrogate the impact of this pro-autoimmune allele on anti-viral immunity during Lymphocytic Choriomeningitis Virus clone 13 (LCMV-cl13) infection. Mice homozygous for this allele (PEP-619WW) clear the LCMV-cl13 virus whereas wildtype (PEP-WT) mice cannot. This is associated with enhanced anti-viral CD4 T cell responses and a more immunostimulatory CD8α- cDC phenotype. Adoptive transfer studies demonstrated that PEP-619WW enhanced anti-viral CD4 T cell function through virus-specific CD4 T cell intrinsic and extrinsic mechanisms. Taken together, our data show that the pro-autoimmune allele of Ptpn22 drives a beneficial anti-viral immune response thereby preventing what is normally a chronic virus infection.

Androgen Receptor regulates Ptpn22.

Abstract The need to rear the offspring necessitated the evolution of female’s immune system to mount stronger responses than males. One consequence of it is that major autoimmune diseases manifest in a sex biased manner with a predominance in females. However, mechanisms underlying the bias have not been clearly defined. We investigated the molecular mechanisms by which male sex hormones (androgens) regulate αβ T cell function in sex biased autoimmunity. We identified Ptpn22, a gene encoding a lymphoid-specific phosphatase that negatively regulates proximal TCR signaling events, as a direct target of a transcription factor Androgen Receptor (AR) in T cells. In T cells isolated from sham-operated or castrated mice, transcription of Ptpn22 correlated with the presence of androgens. Furthermore, stimulation of Jurkat T cells with AR agonist resulted in induction of Ptpn22 transcription only in the presence of AR. Deletion of Ptpn22 in the B6.NZM mouse model of Systemic Lupus Erythematosus (SLE) led to exacerbation of autoimmunity accompanied by the loss of sexual dimorphism. We identified an androgen response element (ARE) in the 5′ UTR of Ptpn22 and found that its CRISPR/Cas9-mediated mutation enhanced both in vitro and in vivo the autoreactivity of T cells in NOD/ShiLtJ mouse model of Type I Diabetes (T1D). In humans, PTPN22 R620W mutation associated with several autoimmune disorders inversely correlated with the sexual dimorphism of autoimmunity. Thus, the ‘wild-type’ common allele of PTPN22 is likely to be involved in sex bias in autoimmune conditions. NIH grant R01 AI 127411

Proautoimmune Allele of Tyrosine Phosphatase, PTPN22, Enhances Tumor Immunity.

The 1858C>T allele of the tyrosine phosphatase PTPN22 (causing amino acid substitution R620W in encoded protein lymphoid tyrosine phosphatase) is present in 5-10% of the North American population and is strongly associated with numerous autoimmune diseases. Although much research has been done to define how this allele potentiates autoimmunity, the influence PTPN22 and its proautoimmune allele have in tumor immunity is poorly defined. To interrogate the role this allele may have in the antitumor immune response, we used CRISPR/Cas9 to generate mice in which the ortholog of lymphoid tyrosine phosphatase, PEST domain-enriched protein (PEP), is mutated at position 619 to produce the relevant proautoimmune mutation (R619W). Results of this study show that mice homozygous for this alteration (PEP-619WW) resist tumor growth as compared with wild-type mice. Consistent with these results, tumors from PEP-619WW mice have more CD45 infiltrates containing more activated CD8 T cells and CD4 T cells. In addition, there are more conventional dendritic cell type 1 (cDC1) cells and fewer myeloid-derived suppressor cells in tumors from PEP-619WW mice. Interestingly, the tumor-infiltrating PEP-619WW cDC1 cells have decreased PD-L1 expression compared with cDC1 cells from PEP-wild-type mice. Taken together, our data show that the proautoimmune allele of Ptpn22 drives a strong antitumor response in innate and adaptive immune cells resulting in superior control of tumors.

Autoimmunity-Associated PTPN22 Polymorphisms in Latent Autoimmune Diabetes of the Adult Differ from Those of Type 1 Diabetes Patients

Background: A portion of adults with humoral immune changes have clinical diabetes that is initially not insulin-requiring (latent autoimmune diabetes of the adult, LADA). One of the genes strongly associated with autoimmune diabetes is PTPN22. We hypothesized that the manifestation and clinical features of LADA are linked to functional variants of PTPN22. Methods: We genotyped allelic frequencies of 1 protective and 3 risk-associated PTPN22 variants in 156 Czech LADA patients, 194 type 2 diabetes mellitus patients with LADA-like progression to insulinotherapy and 324 type 1 diabetes mellitus patients, and subsequently examined the associations of PTPN22 variants with the expression of autoantibodies and other clinical features of LADA. Results: We challenged the paradigm that stated that the PTPN22 c.1858T allele serves as a risk allele for LADA, although we confirmed its risk status in the geographically matched T1DM cohort. In contrast, the frequencies of other PTPN22 alleles (c.–1123C, c.788A and c.1970-852C) differed significantly from the healthy controls. We confirmed gender-related differences in the frequency of some PTPN22 polymorphisms (but not c.1858C>T) in LADA. The particular PTPN22 alleles and genotypes were associated with specific clinical features of the examined patients (autoantibodies, HbA_1c and age at diagnosis of diabetes). Conclusions: The variability in PTPN22 haplotypes suggests that the genetic signature of LADA is independent and should not be considered a hybrid form of T1DM and T2DM. Further studies should elucidate the associations with clinical characteristics of the LADA patients and focus on the newly emerging types of diabetes with the disease onset in early to mid-adulthood.

Use of short interfering RNA delivered by cationic liposomes to enable efficient down-regulation of PTPN22 gene in human T lymphocytes.

Type 1 diabetes and thyroid disease are T cell-dependent autoimmune endocrinopathies. The standard substitutive administration of the deficient hormones does not halt the autoimmune process; therefore, development of immunotherapies aiming to preserve the residual hormonal cells, is of crucial importance. PTPN22 C1858T mutation encoding for the R620W lymphoid tyrosine phosphatase variant, plays a potential pathophysiological role in autoimmunity. The PTPN22 encoded protein Lyp is a negative regulator of T cell antigen receptor signaling; R620W variant, leading to a gain of function with paradoxical reduced T cell activation, may represent a valid therapeutic target. We aimed to develop novel wild type PTPN22 short interfering RNA duplexes (siRNA) and optimize their delivery into Jurkat T cells and PBMC by using liposomal carriers. Conformational stability, size and polydispersion of siRNA in lipoplexes was measured by CD spectroscopy and DLS. Lipoplexes internalization and toxicity evaluation was assessed by confocal microscopy and flow cytometry analysis. Their effect on Lyp expression was evaluated by means of Western Blot and confocal microscopy. Functional assays through engagement of TCR signaling were established to evaluate biological consequences of down-modulation. Both Jurkat T cells and PBMC were efficiently transfected by stable custom lipoplexes. Jurkat T cell morphology and proliferation was not affected. Lipoplexes incorporation was visualized in CD3+ but also in CD3- peripheral blood immunotypes without signs of toxicity, damage or apoptosis. Efficacy in affecting Lyp protein expression was demonstrated in both transfected Jurkat T cells and PBMC. Moreover, impairment of Lyp inhibitory activity was revealed by increase of IL-2 secretion in culture supernatants of PBMC following anti-CD3/CD28 T cell receptor-driven stimulation. The results of our study open the pathway to future trials for the treatment of autoimmune diseases based on the selective inhibition of variant PTPN22 allele using lipoplexes of siRNA antisense oligomers.

Rs2476601 polymorphism in PTPN22 is associated with Crohn's disease but not with ulcerative colitis: a meta-analysis of 16,838 cases and 13,356 controls.

BackgroundAlthough the rs2476601 polymorphism of PTPN22 has been reported to be a susceptibility gene for Crohn’s disease (CD), results from different studies vary and remain inconclusive. Also, no association has been found between rs2476601 and the risk of ulcerative colitis (UC). The aim of this meta-analysis was to investigate the association between this PTPN22 polymorphism (rs2476601) and the risk of inflammatory bowel disease, UC and CD.MethodsWe performed a meta-analysis by identifying relevant candidate gene-based studies from EMBASE and MEDLINE. Odds ratios (OR) and 95% confidence intervals (CI) were calculated to estimate the strength of associations between rs2476601 and inflammatory bowel diseases, using a fixed effect or random effect model. Publication bias was also assessed.ResultsBy pooling 14 different studies, 13,356 controls, 8182 patients with CD, and 8656 with UC were included. We found that the T allele of PTPN22 was not significantly associated with a higher risk of developing UC (OR 1.06, 95%CI 0.98-1.14) but was associated with a decreased risk of developing CD (OR 1.28, 95%CI 1.17-1.40). The T allele in rs2476601 lowered the risk of CD by 22%.ConclusionThis study shows that PTPN22 (rs2476601) is significantly associated with the risk of developing CD, but has no association with UC. This suggests that these diseases have different pathways involved in their pathophysiology.

The association of PTPN22 (rs2476601) and IL2RA (rs11594656) polymorphisms with T1D in Egyptian children

BackgroundType 1 diabetes mellitus (T1D) is a T cell-mediated autoimmune disease characterized by the destruction of pancreatic β cells. PTPN22 and IL2RA polymorphisms have been found to be associated with several autoimmune diseases including T1D. AimsWe aimed to elucidate the role of PTPN22 and IL2RA polymorphisms in predisposition of T1D in Egyptian children. MethodsWe studied 150 children and adolescents with T1D and 165 healthy controls. The PTPN22 (rs2476601) and IL2RA (rs11594656) polymorphisms were genotyped using polymerase chain reaction. ResultsWe found that carriers of the T allele of PTPN22 were significantly more likely to develop T1D (OR=2.2, 95% CI=1.2–4, P=0.01). Also, the carrier of TT genotype and T allele of IL2RA more likely to develop T1D (OR=2.8, 1.4, respectively, P=0.03). There was a statistically significant association between T allele of PTPN22 gene and females ⩽10years old at the onset of diabetes (OR=4, 95% CI=1.2–13.4, P=0.019). ConclusionThis study suggests a possible association between the T allele of PTPN22 gene and TT genotype of IL2RA with T1D in studied Egyptian children, especially, females with early onset diabetes who carried the 1858T allele.

Detection of anti-non bilayer phospholipids arragements antibodies and genotyping in patients with systemic lupus erythematosus and secondary antiphospholipid syndrome

Abstract Phospholipids are the main structural constituents of all cell membranes, their form the smooth bilayer matrix that delimited cells in which membrane proteins are located. However, some anionic phospholipids can lead to the formation of nonbilayer phospholipid arrangements (NPA) within the bilayer. NPA are transient but when they are stabilized by the drugs chlorpromazine, procainamide or hydralazine, which produced lupus-like disease in humans, they induce a disease resembling human lupus in mice. Mice present IgM and IgG antibodies against NPA which appear 4 weeks before that autoantibodies against cardiolipin, histones, nuclear and lupus anticoagulant antibodies. Mice also present histopathological abnormalities in the skin and kidneys similar to those observed in systemic lupus erythematosus (SLE). We proposed that the recognition of NPA by anti-NPA antibodies and after by the classical complement pathway causes cell lysis exposing intracellular antigens with the consequent formation of autoantibodies. Antibodies against NPA have been described in patients with SLE, lepromatous leprosy and hypertensive disorders of pregnancy. The present investigation is a clinical study not randomized, prospective, in Mexican mestizos patients of any sex and age, with SLE or with secondary antiphospholipid syndrome in which we found that the elevated levels of anti-NPA antibodies could trigger autoimmunity in these diseases and we determined that high titers lead to increased activity and correlate with the expression of HLA-DR, HLA-DQ, HLA-A, HLA-B, IL-10 (-1082G/A, -819C/T, -592C/A) and PTPN22 (+1858C/T) alleles. All clinic assays were approved by the Committee of Bioethics of our Institutions.

Association of P53 Codon 72 with Colon Cancer: the Role of Genetic Factors

AIM: Studies on the association between p53 codon 72 and colon cancer have given contrasting results: in some populations a positive association has been found with *Pro variant, in other with *Arg variant and in other populations no association has been observed .We have studied the possible effect of genetic variability within four common polymorphisms on the association between p53 codon 72 and colon cancer. METHODS AND MATERIAL: 106 subjects with colon cancer and 476 controls from the White population of Rome were studied. p53 codon 72, ACP1, PTPN22, ADA2 and ADA6 polymorphisms were determined by DNA analysis. Statistical analyses were carried out by SPSS programs. RESULTS: The proportions of the joint genotypes of *Pro allele carriers with *B/*B genotype of ACP1, with carriers of *T allele of PTPN22, with the ADA1*1/*1 genotype and with carriers of ADA6*1 allele are higher in colon cancer than in controls. A statistically significant positive correlation is observed in colon cancer between the proportion of *Pro allele carriers and the number of the four genetic factors considered. Sex and cancer grade influence this correlation. CONCLUSIONS: Common genetic polymorphisms influence the strength of correlation between p53 codon 72 and colon cancer suggesting a possible explanation of the contrasting result observed between different populations. Moreover, the results support the multi-factorial origin of cancer.

Ptpn22 and Cd2 Variations Are Associated with Altered Protein Expression and Susceptibility to Type 1 Diabetes in Nonobese Diabetic Mice.

By congenic strain mapping using autoimmune NOD.C57BL/6J congenic mice, we demonstrated previously that the type 1 diabetes (T1D) protection associated with the insulin-dependent diabetes (Idd)10 locus on chromosome 3, originally identified by linkage analysis, was in fact due to three closely linked Idd loci: Idd10, Idd18.1, and Idd18.3. In this study, we define two additional Idd loci—Idd18.2 and Idd18.4—within the boundaries of this cluster of disease-associated genes. Idd18.2 is 1.31 Mb and contains 18 genes, including Ptpn22, which encodes a phosphatase that negatively regulates T and B cell signaling. The human ortholog of Ptpn22, PTPN22, is associated with numerous autoimmune diseases, including T1D. We, therefore, assessed Ptpn22 as a candidate for Idd18.2; resequencing of the NOD Ptpn22 allele revealed 183 single nucleotide polymorphisms with the C57BL/6J (B6) allele—6 exonic and 177 intronic. Functional studies showed higher expression of full-length Ptpn22 RNA and protein, and decreased TCR signaling in congenic strains with B6-derived Idd18.2 susceptibility alleles. The 953-kb Idd18.4 locus contains eight genes, including the candidate Cd2. The CD2 pathway is associated with the human autoimmune disease, multiple sclerosis, and mice with NOD-derived susceptibility alleles at Idd18.4 have lower CD2 expression on B cells. Furthermore, we observed that susceptibility alleles at Idd18.2 can mask the protection provided by Idd10/Cd101 or Idd18.1/Vav3 and Idd18.3. In summary, we describe two new T1D loci, Idd18.2 and Idd18.4, candidate genes within each region, and demonstrate the complex nature of genetic interactions underlying the development of T1D in the NOD mouse model.

Non-HLA type 1 diabetes genes modulate disease risk together with HLA-DQ and islet autoantibodies.

The possible interrelations between HLA-DQ, non-HLA single nucleotide polymorphisms (SNPs) and islet autoantibodies were investigated at clinical onset in 1-34 year old type 1 diabetes (T1D) patients (n=305) and controls (n=203). Among the non-HLA SNPs reported by the Type 1 Diabetes Genetics Consortium, 24% were supported in this Swedish replication set including that the increased risk of minor PTPN22 allele and high risk HLA was modified by GAD65 autoantibodies. The association between T1D and the minor AA+AC genotype in ERBB3 gene was stronger among IA-2 autoantibody-positive patients (comparison p=0.047). The association between T1D and the common insulin (AA) genotype was stronger among insulin autoantibody (IAA)-positive patients (comparison p=0.008). In contrast, the association between T1D and unidentified 26471 gene was stronger among IAA-negative (comparison p=0.049) and IA-2 autoantibody-negative (comparison p=0.052) patients. Finally, the association between IL2RA and T1D was stronger among IAA-positive than among IAA-negative patients (comparison p=0.028). These results suggest that the increased risk of T1D by non-HLA genes is often modified by both islet autoantibodies and HLA-DQ. The interactions between non-HLA genes, islet autoantibodies and HLA-DQ should be taken into account in T1D prediction studies as well as in prevention trials aimed at inducing immunological tolerance to islet autoantigens.

Genetics of vasculitis.

We aim to give an overview of the recent progress in the knowledge of the genetic component of vasculitides. Using a state-of-the-art imputation method to analyse the major histocompatibility complex (MHC) region, Ombrello and colleagues narrowed down the association between human leukocyte antigen (HLA)-B51 and Behçet's disease to a model of five amino acids of the HLA-B molecule involved in the binding of the antigen, the interactions with receptors on CD8 T cells and natural killer cells, and the signal peptide of HLA-B, suggesting a crucial role of the cellular cytotoxicity on this disease. Other recent genetic studies have identified several loci with strong effects on vasculitis predisposition, most of them representing important players in the immune and inflammatory response. These associations include ERAP1, CCR1-CCR3, STAT4, KLRC4, GIMAP4, and TNFAIP3 in Behçet's disease; BLK and CD40 in Kawasaki disease; SERPINA1 and SEMA6A in antineutrophil cytoplasmic antibody associated vasculitides; IL12B and FCGR2A/ FCGR2A in Takayasu arteritis; and CECR1 in a newly defined vascular inflammatory syndrome associated with adenosine deaminase (ADA2) deficiency. Although other vasculitides, such as giant cell arteritis (GCA) or immunoglobulin A vasculitis, have not benefitted by the great advantage of the large-scale genetic analyses yet, some interesting associations have been recently suggested, such as the classical functional PTPN22 allele rs2476601 (R620W) with GCA. The analysis of high-throughput genotyping and exome-sequencing data has produced a considerable advance in the identification of consistent genetic risk factors in vasculitides during the last 3 years. Further collaborative efforts, which will increase the sample size, and the use of custom arrays like the immunochip, will definitively help to better understand the genetic basis of vasculitides and to identify the common and specific molecular pathways underlying their pathophysiology.

The tyrosine phosphatase PTPN22 discriminates weak self peptides from strong agonist TCR signals.

T cells must be tolerant of self-antigens to avoid autoimmunity, but responsive to foreign-antigens to provide protection against infection. We found that in both naive and effector T cells, the tyrosine phosphatase, Ptpn22 limits T cell receptor signaling by weak agonist and self-antigens, while not impeding responses to strong agonist antigens. T cells lacking Ptpn22 show enhanced conjugate formation with antigen presenting cells pulsed with weak peptides, leading to their activation and production of inflammatory cytokines. This effect is exacerbated under conditions of lymphopenia with the formation of potent memory T cells in the absence of Ptpn22. These data address how loss of function PTPN22 alleles can lead to expansion of effector/memory T cells and a predisposition to human autoimmunity.

Type 1 diabetes mellitus. Comparison between the association with PTPN22 genotype and the association with ACP1–ADA1 joint genotype

AimsT1D has been found associated with PTPN22 and with ACP1–ADA1 joint genotype. In the present note we have collected further data to evaluate the relative importance of the two systems and to search for possible interaction of PTPN22 with ACP1–ADA1 joint genotype. MethodsWe have studied 314 children with T1D and 770 controls from the White population of Central Italy. ACP1, ADA1 and PTPN22 genotypes were determined by DNA analysis. Chi square test of independence was performed by SPSS program and three way contingency analysis by a log-linear model. ResultsBoth carriers of *T allele of PTPN22 and subjects with ACP1 *A/*A and *A/*B genotypes carrying ADA1 *2 allele show an increase of susceptibility to T1D. There is evidence of additive effect (p=0.0002) but not of epistatic interaction. The association of T1D with ACP1–ADA1 joint genotype is stronger (OR=2.494, 95% C.I. 1.509–4.122) as compared to that with PTPN22 (OR=1.825, 95% C.I. 1.951–2.859). ConclusionsIt has been suggested that the *T variant of PTPN22 inhibits T cell receptor signaling leading to failure to delete autoreactive T cells during intrathymic selection resulting in increased susceptibility to autoimmune disorders. The joint genotype ACP1 *A/*A and *A/*B carrying the ADA1 *2 allele shows a decreased activity of ACP1 resulting in a lowering of Zap70 activity that may decrease T cell receptor signaling with an additive effects to the inhibition due to the *T variant of PTPN22.

THU0018 Discrimination Analysis of Multiple Genetic Risk Markers Associated with Rheumatoid Arthritis in Slovakia

BackgroundSeveral genes have been identified so far in the pathogenesis of rheumatoid arthritis (RA). The most important region is the Human Leukocyte Antigen (HLA) that contributes to approximately half of...

Ptpn22 promotes immunization responses to Influenza A (P4043)

Abstract A variant allele of PTPN22 is a potent susceptibility factor for autoimmune diseases, including Rheumatoid Arthritis and Type I Diabetes. Ptpn22 is required in myeloid cells for selective promotion of Toll-Like Receptor signaling leading to Type I IFN production. Since Type I IFN are essential for anti-viral immunity and for efficient responses to viral immunization, we investigated the role of PTPN22 in response to vaccination. We tested the ability of Ptpn22 knockout mice to mount a protective immune response to vaccination against Influenza A virus. We found that Ptpn22 is required for efficient generation of both influenza-specific cytotoxic T lymphocyte and neutralizing humoral responses after vaccination with inactivated influenza. Further, upon challenge with live influenza, vaccinated Ptpn22 KO animals exhibit increased mortality, suggesting that defects in antibody and CTL responses associated with Ptpn22 deficiency result in decreased protection engendered by inactivated influenza vaccination. These findings indicate a requirement for Ptpn22 in protective immune responses to influenza vaccine. Moreover, they suggest that further studies of vaccine responsiveness should be mounted in human carriers of the disease-associated PTPN22 variant, since such carriers exhibit diminished Toll-Like Receptor-induced Type I IFN production by myeloid cells.

Expansion of CD4+CD25+FOXP3+ regulatory T cells in infants of mothers with type 1 diabetes.

Reduced risk for type 1 diabetes (T1D) has been reported in the offspring of mothers with T1D when compared with children of affected fathers. To evaluate the hypothesis that exposure of the offspring to maternal insulin therapy induces regulatory mechanisms in utero, we compared the FOXP3 expressing regulatory T cells in cord blood (CB) of infants born to mothers with or without T1D. Cord blood mononuclear cells (CBMCs) from 20 infants with maternal T1D and from 20 infants with an unaffected mother were analyzed for the numbers of CD4+CD25+FOXP3+ cells ex vivo and after in vitro stimulation with human insulin by flow cytometry. The mRNA expression of FOXP3, NFATc2, STIM1, interleukin (IL)-10, and transforming growth factor (TGF)-β was measured by real-time reverse transcription polymerase chain reaction. The percentage of FOXP3+ cells in CD4+CD25(high) cells was higher in the CB of the infants with maternal T1D when compared with the infants of unaffected mothers (p = 0.023). After in vitro insulin stimulation an increase in the percentage of FOXP3+ cells in CD4+CD25(high) cells (p = 0.0002) as well as upregulation of FOXP3, NFATc2, STIM1, IL-10, and TGF-β transcripts in CBMCs (p < 0.013 for all; Wilcoxon test) was observed only in the offspring of mothers with T1D, in whom the disease-related PTPN22 allele was associated with reduced STIM1 and NFATc2 response in insulin-stimulated CBMCs (p = 0.007 and p = 0.014). We suggest that maternal insulin treatment induces expansion of regulatory T cells in the fetus, which might contribute to the lower risk of diabetes in children with maternal vs. paternal diabetes.

The establishment of early B cell tolerance in humans: lessons from primary immunodeficiency diseases

Patients with primary immunodeficiency (PID) provide rare opportunities to study the impact of specific gene mutations on the regulation of human B cell tolerance. Alterations in B cell receptor and Toll-like receptor signaling pathways result in a defective central checkpoint and a failure to counterselect developing autoreactive B cells in the bone marrow. In contrast, CD40L- and MHC class II-deficient patients only displayed peripheral B cell tolerance defects, suggesting that decreased numbers of regulatory T cells and increased concentration of B cell activating factor (BAFF) may interfere with the peripheral removal of autoreactive B cells. The pathways regulating B cell tolerance identified in PID patients are likely to be affected in patients with rheumatoid arthritis, systemic lupus erythematosus, and type 1 diabetes who display defective central and peripheral B cell tolerance checkpoints. Indeed, risk alleles encoding variants altering BCR signaling, such as PTPN22 alleles associated with the development of these diseases, interfere with the removal of developing autoreactive B cells. Hence, insights into B cell selection from PID patients are highly relevant to the understanding of the etiology of autoimmune conditions.