Search

IMPORTANCE: The SARS-CoV-2 variant B.1.1.529 (Omicron) escapes neutralizing antibodies elicited after COVID-19 vaccination, while T-cell responses might be better conserved. It is crucial to assess how a third vaccination modifies these responses, particularly for immunocompromised patients with readily impaired antibody responses. OBJECTIVE: To determine T-cell responses to the Omicron spike protein in anti-CD20–treated patients with multiple sclerosis (MS) before and after a third messenger RNA COVID-19 vaccination. DESIGN, SETTING, AND PARTICIPANTS: In this prospective cohort study conducted from March 2021 to November 2021 at the University Hospital Geneva, adults with MS receiving anti-CD20 treatment (ocrelizumab) were identified by their treating neurologists and enrolled in the study. A total of 20 patients received their third dose of messenger RNA COVID-19 vaccine and were included in this analysis. INTERVENTIONS: Blood sampling before and 1 month after the third vaccine dose. MAIN OUTCOMES AND MEASURES: Quantification of CD4 and CD8 (cytotoxic) T cells specific for the SARS-CoV-2 spike proteins of the vaccine strain as well as the Delta and Omicron variants, comparing frequencies before and after the third vaccine dose. RESULTS: Of 20 included patients, 11 (55%) were male, and the median (IQR) age was 45.8 (37.8-53.3) years. Spike-specific CD4 and CD8 T-cell memory against all variants were maintained in 9 to 12 patients 6 months after their second vaccination, albeit at lower median frequencies against the Delta and Omicron variants compared with the vaccine strain (CD8 T cells: Delta, 83.0%; 95% CI, 73.6-114.5; Omicron, 78.9%; 95% CI, 59.4-100.0; CD4 T cells: Delta, 72.2%; 95% CI, 67.4-90.5; Omicron, 62.5%; 95% CI, 51.0-89.0). A third dose enhanced the number of responders to all variants (11 to 15 patients) and significantly increased CD8 T-cell responses, but the frequencies of Omicron-specific CD8 T cells remained 71.1% (95% CI, 41.6-96.2) of the responses specific to the vaccine strain. CONCLUSIONS AND RELEVANCE: In this cohort study of patients with MS treated with ocrelizumab, there were robust T-cell responses recognizing spike proteins from the Delta and Omicron variants, suggesting that COVID-19 vaccination in patients taking B-cell–depleting drugs may protect them against serious complications from COVID-19 infection. T-cell response rates increased after the third dose, demonstrating the importance of a booster dose for this population.

Background: The excess risk of cardiovascular disease associated with a wide array of infectious diseases is unknown. We quantified the short- and long-term risk of major cardiovascular events in people with severe infection and estimated the population-attributable fraction. Methods: We analyzed data from 331 683 UK Biobank participants without cardiovascular disease at baseline (2006-2010) and replicated our main findings in an independent population from 3 prospective cohort studies comprising 271 329 community-dwelling participants from Finland (baseline 1986-2005). Cardiovascular risk factors were measured at baseline. We diagnosed infectious diseases (the exposure) and incident major cardiovascular events after infections, defined as myocardial infarction, cardiac death, or fatal or nonfatal stroke (the outcome) from linkage of participants to hospital and death registers. We computed adjusted hazard ratios (HRs) and 95% CIs for infectious diseases as short- and long-term risk factors for incident major cardiovascular events. We also calculated population-attributable fractions for long-term risk. Results: In the UK Biobank (mean follow-up, 11.6 years), 54 434 participants were hospitalized for an infection, and 11 649 had an incident major cardiovascular event at follow-up. Relative to participants with no record of infectious disease, those who were hospitalized experienced increased risk of major cardiovascular events, largely irrespective of the type of infection. This association was strongest during the first month after infection (HR, 7.87 [95% CI, 6.36-9.73]), but remained elevated during the entire follow-up (HR, 1.47 [95% CI, 1.40-1.54]). The findings were similar in the replication cohort (HR, 7.64 [95% CI, 5.82-10.03] during the first month; HR, 1.41 [95% CI, 1.34-1.48] during mean follow-up of 19.2 years). After controlling for traditional cardiovascular risk factors, the population-attributable fraction for severe infections and major cardiovascular events was 4.4% in the UK Biobank and 6.1% in the replication cohort. Conclusions: Infections severe enough to require hospital treatment were associated with increased risks for major cardiovascular disease events immediately after hospitalization. A small excess risk was also observed in the long-term, but residual confounding cannot be excluded. CC BY 4.0Correspondence to: Pyry Sipilä, Clinicum, Department of Public Health, PO Box 20, FI-00014 University of Helsinki, Finland. Email pyry.sipila@helsinki.fiAcknowledgmentsThis research was conducted using data from the UK Biobank (https://www.ukbiobank.ac.uk/) via application 60565.Sources of FundingThis work was funded in whole, or in part, by grants from NordForsk (75021), Academy of Finland (329202 and 350426), Helsinki Institute of Life Science, Emil Aaltonen Foundation, Finnish Medical Foundation, Päivikki and Sakari Sohlberg Foundation, Finnish Foundation for Cardiovascular Research (a86898), US National Institute on Aging (R01AG056477, 1R56AG052519-01, and 1R01AG052519-01A1), UK Medical Research Council (MRC S011676/1, R024227/1, and MR/P023444/1), and Wellcome Trust (201440/Z/16/Z and 221854/Z/20/Z). The funders had no role in study design, data collection, analysis, or interpretation, or writing of the report or decision to submit it for publication.DisclosuresDr Sipilä reports grant support during the conduct of the study from NordForsk (75021), Academy of Finland (311492 and 329202), Helsinki Institute of Life Science, Emil Aaltonen Foundation, and Finnish Medical Foundation. Dr Lindbohm reports grant support during the conduct of the study from the Academy of Finland (339568) and Päivikki and Sakari Sohlberg Foundation. Dr Batty reports grant support from the UK Medical Research Council (MR/P023444/1) and US National Institute on Aging (1R56AG052519-01 and 1R01AG052519-01A1). Dr Vahtera reports grant support from the Academy of Finland (321409 and 329240) and NordForsk (75021). Dr Nyberg reports grant support from NordForsk (75021). Dr Warren-Gash reports support from Wellcome Fellowship (201440/Z/16/Z). Dr Kivimäki reports grant support during the conduct of the study from NordForsk (75021), UK Medical Research Council (MRC S011676/1 and R024227/1), US National Institute on Aging (R01AG056477), Academy of Finland (329202 and 350426), Finnish Foundation for Cardiovascular Research (a86898), Finnish Work Environment Fund (190424), and Wellcome Trust (221854/Z/20/Z). The other authors report no conflicts.

Funding Information: We thank the nurses of the Transplantation Unit of Helsinki University Central Hospital, HiLife Flow Cytometry Unit of University of Helsinki, and Tamás Bazsinka for technical support. This study has been funded by Emil Aaltonen Foundation, Finnish Medical Foundation, Foundation for Pediatric Research, Biomedicum Helsinki Foundation, Roche Research grant, the MD PhD program of the University of Helsinki, and the Competitive State Research Financing of Responsibility Area of Helsinki University Hospital (TYH2019307). Publisher Copyright: © 2022 The Authors. European Journal of Immunology published by Wiley-VCH GmbH. Long-term T-cell memory is dependent on the maintenance of memory T cells in the lymphoid tissues, and at the surface interfaces that provide entry routes for pathogens. However, much of the current information on human T-cell memory is based on analyzing circulating T cells. Here, we have studied the distribution and age-related changes of memory T-cell subsets in samples from blood, mesenteric LNs, spleen, and ileum, obtained from donors ranging in age from 5 days to 67 years of age. Our data show that the main reservoir of polyclonal naive cells is found in the LNs, and the resting memory subsets capable of self-renewal are also prominent there. In contrast, nondividing but functionally active memory subsets dominate the spleen, and especially the ileum. In general, the replacement of naive cells with memory subsets continues throughout our period of observation, with no apparent plateau. In conclusion, the analysis of lymphoid and nonlymphoid tissues reveals a dynamic pattern of changes distinct to each tissue, and with substantial differences between CD4+ and CD8+ compartments.

A highly diverse repertoire of T cell antigen receptors (TCR) is created in the thymus by recombination of gene segments and the insertion or deletion of nucleotides at the junctions. Using next-generation TCR sequencing we define here the features of recombination and selection in the human TCR alpha and TCR beta locus, and show that a strikingly high proportion of the repertoire is shared by unrelated individuals. The thymic TCRa nucleotide repertoire was more diverse than TCR beta, with 4.1 x 10(6) vs. 0.81 x 10(6) unique clonotypes, and contained nonproductive clonotypes at a higher frequency (69.2% vs. 21.2%). The convergence of distinct nucleotide clonotypes to the same amino acid sequences was higher in TCRa than in TCR beta repertoire (1.45 vs. 1.06 nucleotide sequences per amino acid sequence in thymus). The gene segment usage was biased, and generally all individuals favored the same genes in both TCR alpha and TCR beta loci. Despite the high diversity, a large fraction of the repertoire was found in more than one donor. The shared fraction was bigger in TCR alpha than TCR beta repertoire, and more common in in-frame sequences than in nonproductive sequences. Thus, both biases in rearrangement and thymic selection are likely to contribute to the generation of shared repertoire in humans.

The Ikaros family transcription factors regulate lymphocyte development. Loss-of-function variants in

We have analyzed T cell receptor repertoires in a unique set of thymus samples from a pair of monozygotic twins. While genetics affect the V(D)J rearrangement and generation of junctional sequences, the thymic selections seem largely stochastic and import no detectable inheritable effect at clonal level.

The IKAROS family transcription factors regulate lymphocyte development. Loss-of-function variants in IKZF1 cause primary immunodeficiency, but IKAROS family members IKZF2 and IKZF3 have not yet been associated with immunodeficiency yet. Here, we describe a pedigree with a heterozygous truncating variant in IKZF2, encoding the translational activator and repressor HELIOS which is highly expressed in regulatory T cells and effector T cells, particularly of the CD8+ T cell lineage. Protein-protein interaction analysis revealed that the variant abolished HELIOS dimerizations as well as binding to members of the Mi-2/NuRD chromatin remodeling complex. Patients carrying the IKZF2 variant presented with a combined immunodeficiency phenotype characterized by recurrent upper respiratory infections, thrush and mucosal ulcers, as well as chronic lymphadenopathy. With extensive immunophenotyping, functional assays, and transcriptional analysis we show that reduced HELIOS expression was associated with chronic T cell activation and increased production of pro-inflammatory cytokines both in effector and regulatory T cells. Lymph node histology from patients indicated dysregulated germinal center reactions. Moreover, affected individuals displayed profoundly reduced circulating MAIT cell numbers. In summary, we show that this novel loss-of-function variant in HELIOS leads to an immunodeficiency with signs of immune overactivation.One sentence summaryTruncating variant of HELIOS causes immunodeficiency with signs of immune overactivation.

The T-cell receptor (TCR) repertoire is generated in a semistochastic process of gene recombination and pairing of TCRα to TCRβ chains with the estimated total TCR diversity of >108. Despite this high diversity, similar or identical TCR chains are found to recur in immune responses. Here, we analyzed the thymic generation of TCR sequences previously associated with recognition of self- and nonself-antigens, represented by sequences associated with autoimmune diabetes and HIV, respectively. Unexpectedly, in the CD4+ compartment TCRα chains associated with the recognition of self-antigens were generated in significantly higher numbers than TCRα chains associated with the recognition of nonself-antigens. The analysis of the circulating repertoire further showed that these chains are not lost in negative selection nor predominantly converted to the regulatory T-cell lineage. The high abundance of self-reactive TCRα chains in multiple individuals suggests that the human thymus has a predilection to generate self-reactive TCRα chains independently of the HLA-type and that the individual risk of autoimmunity may be modulated by the TCRβ repertoire associated with these chains. publishedVersion

BACKGROUND: Infections have been hypothesised to increase the risk of dementia. Existing studies have included a narrow range of infectious diseases, relied on short follow-up periods, and provided little evidence for whether the increased risk is limited to specific dementia subtypes or attributable to specific microbes rather than infection burden. We aimed to compare the risk of Alzheimer's disease and other dementias across a wide range of hospital-treated bacterial and viral infections in two large cohorts with long follow-up periods. METHODS: In this large, multicohort, observational study, the analysis was based on a primary cohort consisting of pooled individual-level data from three prospective cohort studies in Finland (the Finnish Public Sector study, the Health and Social Support study, and the Still Working study) and an independent replication cohort from the UK Biobank. Community-dwelling adults (≥18 years) with no dementia at study entry were included. Follow-up was until Dec 31, 2012, in the Health and Social Support study, Dec 31, 2016, in the public sector study and the Still Working study, and Feb 7, 2018, in the replication cohort. Through record linkage to national hospital inpatient registers, we ascertained exposure to 925 infectious diseases (using the International Classification of Diseases 10th Revision codes) before dementia onset, and identified incident dementia from hospital records, medication reimbursement entitlements, and death certificates. Hazard ratios (HRs) for the associations of each infectious disease or disease group (index infection) with incident dementia were assessed by use of Cox proportional hazards models. We then repeated the analysis after excluding incident dementia cases that occurred during the first 10 years after initial hospitalisation due to the index infection. FINDINGS: From March 1, 1986, to Jan 1, 2005, 260 490 people were included in the primary cohort, and from Dec 19, 2006, to Oct 1, 2010, 485 708 people were included in the replication cohort. In the primary cohort analysis based on 3 947 046 person-years at risk (median follow-up 15·4 years [IQR 9·8-21·0]), 77 108 participants had at least one hospital-treated infection before dementia onset and 2768 developed dementia. Hospitalisation for any infectious disease was associated with increased dementia risk in the primary cohort (adjusted HR [aHR] 1·48 [95% CI 1·37-1·60]) and replication cohort (2·60 [2·38-2·83]). The association remained when analyses were restricted to new dementia cases that occurred more than 10 years after infection (aHR 1·22 [95% CI 1·09-1·36] in the primary cohort, the replication cohort had insufficient follow-up data for this analysis), and when comorbidities and other dementia risk factors were considered. There was evidence of a dose-response association between the number of episodes of hospital-treated infections and dementia risk in both cohorts (ptrend=0·0007). Although the greatest dementia risk was seen for central nervous system (CNS) infections versus no infection (aHR 3·01 [95% CI 2·07-4·37]), excess risk was also evident for extra-CNS infections (1·47 [1·36-1·59]). Although we found little difference in the infection-dementia association by type of infection, associations were stronger for vascular dementia than for Alzheimer's disease (aHR 2·09 [95% CI 1·59-2·75] versus aHR 1·20 [1·08-1·33] in the primary cohort and aHR 3·28 [2·65-4·04] versus aHR 1·80 [1·53-2·13] in the replication cohort). INTERPRETATION: Severe infections requiring hospital treatment are associated with long-term increased risk of dementia, including vascular dementia and Alzheimer's disease. This association is not limited to CNS infections, suggesting that systemic effects are sufficient to affect the brain. The absence of infection specificity combined with evidence of dose-response relationships between infectious disease burden and dementia risk support the hypothesis that increased dementia risk is driven by general inflammation rather than specific microbes. FUNDING: UK Medical Research Council, US National Institute on Aging, Wellcome Trust, NordForsk, Academy of Finland, and Helsinki Institute of Life Science. CC BY 4.0Correspondence to: Dr Pyry N Sipilä, Clinicum, Department of Public Health, University of Helsinki, Helsinki FI-00014, Finland pyry.sipila@helsinki.fiFunding: UK Medical Research Council, US National Institute on Aging, Wellcome Trust, NordForsk, Academy of Finland, and Helsinki Institute of Life Science.

T cell receptor (TCR) is a heterodimer consisting of TCRα and TCRβ chains that are generated by somatic recombination of multiple gene segments. Nascent TCR repertoire undergoes thymic selections where non-functional and potentially autoreactive receptors are removed. During the last years, the development of high-throughput sequencing technology has allowed a large scale assessment of TCR repertoire and multiple analysis tools are now also available. In our recent manuscript, Human thymic T cell repertoire is imprinted with strong convergence to shared sequences[1], we show highly overlapping thymic TCR repertoires in unrelated individuals. In the current Data in Brief article, we provide a more detailed characterization of the basic features of these thymic and related peripheral blood TCR repertoires. The thymus samples were collected from eight infants undergoing corrective cardiac surgery, two of whom were monozygous twins [2]. In parallel with the surgery, a small aliquot of peripheral blood was drawn from four of the donors. Genomic DNA was extracted from mechanically released thymocytes and circulating leukocytes. The sequencing of TCRα and TCRβ repertoires was performed at ImmunoSEQ platform (Adaptive Biotechnologies). The obtained repertoire data were analysed applying relevant features from immunoSEQ® 3.0 Analyzer (Adaptive Biotechnologies) and a freely available VDJTools software package for programming language R [3]. The current data analysis displays the basic features of the sequenced repertoires including observed TCR diversity, various descriptive TCR diversity measures, and V and J gene usage. In addition, multiple methods to calculate repertoire overlap between two individuals are applied. The raw sequence data provide a large database of reference TCRs in healthy individuals at an early developmental stage. The data can be exploited to improve existing computational models on TCR repertoire behaviour as well as in the generation of new models.

SummaryBackgroundInfectious diseases have been hypothesised to increase the risk of dementia. However, the evidence is sparse, captures only a limited range of infectious diseases, and relies on short follow-up periods. We assessed a wide range of severe (hospital-treated) bacterial and viral infections and their subtypes as risk factors for dementia in three large cohorts followed up for almost two decades and replicated the main findings in the UK Biobank.MethodsFor primary analysis, we pooled individual-level data from three prospective cohort studies with a median follow up of 19 years (from 1986-2005 to 2012-2016) and a total of 273 125 dementia-free community-dwelling participants. The replication analysis with the UK Biobank was based on 492 146 individuals (median follow-up 9·0 years from 2006-2010 to 2018). We ascertained exposure to infectious diseases and their subtypes before dementia onset using linked records from national hospital inpatient registers. Incident dementia was identified from linked hospital inpatient and outpatient records, medication reimbursement entitlements, and death certificates.FindingsIn the primary analysis based on 5·3 million person-years at risk, 88 099 participants had a hospital-treated infection before dementia onset and 3064 developed dementia. Gram-negative bacterial infections (hazard ratio [HR] 1·64; 95% confidence interval [CI] 1·25–2·14) and herpesvirus infections (HR 1·96; 95% CI 1·31–2·93) were robustly associated with an increased risk of dementia. For these infections, the relative risk of dementia remained similar when reverse causation and ascertainment biases were minimised by assessing only new dementia cases that occurred more than 10 years after the infection, and when comorbidities and potential confounders were considered. The associations were replicated in the UK Biobank with stronger relations observed for vascular dementia than Alzheimer’s disease. In contrast to gram-negative bacterial and herpesvirus infections, the hazard ratio for all bacterial infections combined attenuated from 1·60 (95% CI 1·48–1·72) to 1·27 (95% CI 1·14–1·41) when bias was minimised. For all viral infections, the corresponding attenuation was from HR 1·63 (95% CI 1·32–2·00) to 1·19 (95% CI 0·87–1·62).InterpretationGram-negative bacterial infections and herpesvirus infections were associated with a moderately increased risk of dementia both in the short- and long-term. Hospital-treated bacterial and viral infections in general had only modest long-term associations with incident dementia.FundingUK Medical Research Council, US National Institute on Aging, NordForsk, Academy of Finland, Helsinki Institute of Life Science.Research in contextEvidence before this studyInfectious diseases have been hypothesised in the aetiology of dementia. We searched PubMed on 2 April 2020 for observational studies and systematic reviews using the search terms ((Alzheimer* OR dementia) AND infectio* AND ((systematic[sb]) OR (Observational Study[ptyp])) without restrictions on language or publication date. We also searched the reference lists and citations of relevant articles. In observational studies, infectious diseases in general and specific bacterial (sepsis, septicaemia, bacteraemia, pneumonia, osteomyelitis, urinary tract infection, cellulitis, syphilis, and Borrelia burgdorferi and Chlamydia pneumoniae infections) and viral infections (hepatitis C infection, HIV) are linked to an increased risk of dementia. Additionally, there was suggestive evidence for associations of herpesvirus infections, Toxoplasma gondii parasite infection, and poor oral health with dementia. However, no large-scale studies assessed a wide range of different types of infectious diseases systematically in a single analytical setting and with adequate control for potential sources of bias, such as reverse causation resulting from the systemic changes related to the preclinical stages of dementia that increase susceptibility to infectious diseases.Added value of this studyIn this multicohort study, the primary analysis was based on individual-level data from 273 125 dementia-free community-dwelling participants with a median follow-up of 19 years. We ascertained 528 different infectious diseases before dementia onset using national hospital inpatient records and categorised them by causative microorganism (bacteria, viruses), disease invasiveness (invasive vs localised bacterial infections), and subtype (extracellular vs intracellular lifestyle and cell wall structure of bacteria, and type of virus). When reverse causation was minimised by analysing only infections that occurred more than 10 years before dementia onset, the relative risk of dementia was modest for all bacterial infections combined (hazard ratio [HR] 1·27; 95% confidence interval [CI] 1·14–1·41) and for all viral infections combined (HR 1·19; 95% CI 0·87–1·62). The associations of bacterial infections with dementia did not differ by the invasiveness of the infection (invasive vs localised infections) or extracellular vs intracellular lifestyle of the causative microorganism. In analysis of specific diagnostic groups, robust and stronger long-term associations with dementia were observed for Gram-negative bacterial infections (HR 1·64, 95% CI 1·25–2·14 for full follow-up; HR 1·67, 95% CI 1·13–2·48 from year 10 onwards) and herpesvirus infections (HR 1·96, 95% CI 1.31–2.93 full follow-up; HR 1·92, 95% CI 1·11–3·32 from year 10 onwards). These associations remained after controlling for comorbidities and potential confounders and were replicated in an independent cohort of 492 146 individuals from the UK Biobank (median follow-up 9·0 years) with stronger relations observed for vascular dementia than Alzheimer’s disease.Implications of all the available evidenceGram-negative bacterial infections and herpesvirus infections seem to be robust long-term risk factors for dementia. Further mechanistic and molecular research is warranted to clarify the potential role of Gram-negative bacterial infections and herpesvirus in neurodegeneration and the aetiology of dementia.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare human autoimmune disorder caused by mutations in the AIRE (autoimmune regulator) gene. Loss of AIRE disrupts thymic negative selection and gives rise to impaired cytotoxic and regulatory T cell populations. To date, CD4(+) T helper (Th) cells remain little studied. This study aims to elucidate their role in APECED pathogenesis.Th cells were explored in ten APECED patients and ten healthy controls using cell culture assays, multiparameter flow cytometry, and transcriptome analysis.The proportions of effector/memory populations were increased while the fraction of naive cells was diminished. The naive population was abnormally activated, with an increased number of cells expressing characteristic Th1, Th2, and Th17 cytokines. No clear deviation to any Th subclass was observed, but transcriptome analysis suggested abnormalities in the Th1 cytokine interferon gamma (IFN-γ) pathway and flow cytometry showed that INF-γ had the highest expression. The augmented INF-γ signaling may promote the function of the putative pathogenic CD8(+) cytotoxic population in the patients. In addition, the frequency of CD4(+) recent thymic emigrants (RTEs) was decreased in the patients, and RTEs also contained cytokine-producing cells at an increased frequency.These data reveal abnormalities in the Th population and suggest that they may in part be traced to premature activation already in the thymus.

A diverse T cell receptor (TCR) repertoire is essential for adaptive immune responses and is generated by somatic recombination of TCR alpha and TCR beta gene segments in the thymus. Previous estimates of the total TCR diversity have studied the circulating mature repertoire, identifying 1 to 3 x 10(6) unique TCR beta and 0.5 x 10(6) TCR alpha sequences. Here we provide the first estimate of the total TCR diversity generated in the human thymus, an organ which in principle can be sampled in its entirety. High-throughput sequencing of samples from four pediatric donors detected up to 10.3 x 10(6) unique TCR beta sequences and 3.7 x 10(6) TCR alpha sequences, the highest directly observed diversity so far for either chain. To obtain an estimate of the total diversity we then used three different estimators, preseq and DivE, which measure the saturation of rarefaction curves, and Chao2, which measures the size of the overlap between samples. Our results provide an estimate of a thymic repertoire consisting of 40 to 70 x 10(6) unique TCR beta sequences and 60 to 100 x 10(6) TCR alpha sequences. The thymic repertoire is thus extremely diverse. Moreover, extrapolation of the data and comparison with earlier estimates of peripheral diversity also suggest that the thymic repertoire is transient, with different clones produced at different times. (C) 2016 Elsevier Ltd. All rights reserved.

Autoimmune polyendocrinopathy - candidiasis - ectodermal dystrophy (APECED) is caused by mutations in the Autoimmune regulator (AIRE) gene and is associated with neutralizing anti-cytokine autoantibodies. We have used an in vivo challenge model to analyze antigen-specific CD4(+) T cell responses. Bacille Calmette-Guerin (BCG)-vaccinated patients and controls were injected tuberculin intradermally, skin blisters were induced by suction on the indurations and on unexposed skin, and the infiltrating cells harvested. The patients had a quantitatively normal CD4(+) T cell response and no significant abnormalities in the expression of T helper type (Th) 1- or Th2-related genes. The expression of interleukin (IL)-22, in contrast, was lower in the patients. Two patients, both with a pre-existing ocular keratopathy, experienced a relapse of keratoconjunctivitis, suggesting a possible immunological basis for this APECED component. Our in vivo data are compatible with a selective IL-22 defect in the activated CD4(+) T cells of APECED patients, affecting also unexposed skin in steady-state conditions.

In addition to its effector functions, complement is an important regulator of adaptive immune responses. Murine studies suggest that complement modulates helper T-cell differentiation, and Th1 responses in particular are impaired in the absence of functional complement. Here, we have studied humoral responses to toxoid vaccines in eight patients with C3 deficiency, representing more than 25% of all the known patients worldwide. Serum cytokine levels were also studied. The patients developed normal Ig responses to tetanus and diphtheria toxoids, but IgE levels were low. The pattern of antigen-specific IgG subclasses was abnormal, with increased Th1-related IgG3 responses, low IgG2, and almost completely undetectable IgG4. The patients also had increased amounts of Th1-related cytokines IL-12p70 and IL-21, and these showed a positive correlation with IgG3 levels. Our results confirm that complement modulates Th differentiation, but reveal a more nuanced outcome than previously reported. Since IgG4 has been linked to tolerogenic responses, the data also suggest that in the absence of functional complement at least some aspects of systemic tolerance are impaired.

Autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED) is a monogenic autoimmune disease that is caused by mutations in the AIRE gene. Murine studies have linked AIRE to thymocyte selection and peripheral deletional tolerance, but the pathogenesis of the human disease remains unclear. In this study, we show that APECED patients have elevated IL-7 levels and a drastically decreased expression of IL-7R on CD8+ T cells. This is associated with increased proliferation and a decreased expression of the negative TCR regulator CD5 in the CD45RO− subset. The CD45RO− cells also display oligoclonal expansions, decreased expression of the lymph node homing factors CCR7 and CD62L, and increased expression of perforin, consistent with the accumulation of highly differentiated effector cells. The CD45RO−CCR7+CD8+ population of cells with markers characteristic of naive phenotype is also skewed, as shown by decreased expression of CD5 and increased expression of perforin. The putative CD31+ recent thymic emigrant population is likewise affected. These data are consistent with IL-7 dysregulation inducing a decreased threshold of TCR signaling and self-antigen–driven proliferation, probably in synergy with the failed thymic selection. The resultant loss of CD8+ T cell homeostasis is likely to play a significant role in the pathogenesis of APECED. Our findings may also hold lessons for other diseases in which the IL-7–IL-7R pathway has emerged as a risk factor.