RESUMEN
Impaired immune functions leading to primary immunodeficiencies often correlate with paradoxical autoimmune complications; patients with hyper-IgM syndromes who are deficient in activation-induced cytidine deaminase (AID), which is required for class-switch recombination and somatic hypermutation, are prone to develop autoimmune diseases. To investigate the impact of AID-deficiency on early B-cell tolerance checkpoints in humans, we tested by ELISA the reactivity of recombinant antibodies isolated from single B cells from AID-deficient patients. New emigrant/transitional and mature naive B cells from AID-deficient patients express an abnormal Ig repertoire and high frequencies of autoreactive antibodies, demonstrating that AID is required for the establishment of both central and peripheral B-cell tolerance. In addition, B-cell tolerance was further breached in AID-deficient patients as illustrated by the detection of anti-nuclear IgM antibodies in the serum of all patients. Thus, we identified a major and previously unsuspected role for AID in the removal of developing autoreactive B cells in humans.
Asunto(s)
Linfocitos B/enzimología , Linfocitos B/inmunología , Citidina Desaminasa/inmunología , Autotolerancia/inmunología , Adolescente , Adulto , Secuencia de Aminoácidos , Anticuerpos Antinucleares/sangre , Anticuerpos Antinucleares/genética , Factor Activador de Células B/sangre , Estudios de Casos y Controles , Niño , Preescolar , Citidina Desaminasa/deficiencia , Citidina Desaminasa/genética , Femenino , Humanos , Inmunoglobulina M/sangre , Inmunoglobulina M/genética , Síndrome de Job/enzimología , Síndrome de Job/genética , Síndrome de Job/inmunología , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Mutación , Células Precursoras de Linfocitos B/enzimología , Células Precursoras de Linfocitos B/inmunología , Autotolerancia/genética , Linfocitos T Reguladores/enzimología , Linfocitos T Reguladores/inmunología , Adulto JovenRESUMEN
Complement receptor 2-negative (CR2/CD21(-)) B cells have been found enriched in patients with autoimmune diseases and in common variable immunodeficiency (CVID) patients who are prone to autoimmunity. However, the physiology of CD21(-/lo) B cells remains poorly characterized. We found that some rheumatoid arthritis (RA) patients also display an increased frequency of CD21(-/lo) B cells in their blood. A majority of CD21(-/lo) B cells from RA and CVID patients expressed germline autoreactive antibodies, which recognized nuclear and cytoplasmic structures. In addition, these B cells were unable to induce calcium flux, become activated, or proliferate in response to B-cell receptor and/or CD40 triggering, suggesting that these autoreactive B cells may be anergic. Moreover, gene array analyses of CD21(-/lo) B cells revealed molecules specifically expressed in these B cells and that are likely to induce their unresponsive stage. Thus, CD21(-/lo) B cells contain mostly autoreactive unresponsive clones, which express a specific set of molecules that may represent new biomarkers to identify anergic B cells in humans.
Asunto(s)
Enfermedades Autoinmunes/inmunología , Linfocitos B/inmunología , Biomarcadores , Anergia Clonal/inmunología , Receptores de Complemento 3d/genética , Receptores de Complemento 3d/inmunología , Adulto , Antígenos CD/inmunología , Antígenos de Diferenciación de Linfocitos T/inmunología , Apoptosis/inmunología , Autoanticuerpos/inmunología , Enfermedades Autoinmunes/genética , Linfocitos B/citología , Antígenos CD40/inmunología , División Celular/inmunología , Anergia Clonal/genética , Femenino , Perfilación de la Expresión Génica , Humanos , Inmunofenotipificación , Ligando Coestimulador de Linfocitos T Inducibles , Subunidad alfa del Receptor de Interleucina-2/inmunología , Lectinas Tipo C/inmunología , Activación de Linfocitos/inmunología , Masculino , Receptores de IgE/inmunología , Proteína Activadora Transmembrana y Interactiva del CAML/inmunología , Adulto JovenRESUMEN
Protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene polymorphisms are associated with many autoimmune diseases. The major risk allele encodes an R620W amino acid change that alters B cell receptor (BCR) signaling involved in the regulation of central B cell tolerance. To assess whether this PTPN22 risk allele affects the removal of developing autoreactive B cells, we tested by ELISA the reactivity of recombinant antibodies isolated from single B cells from asymptomatic healthy individuals carrying one or two PTPN22 risk allele(s) encoding the PTPN22 R620W variant. We found that new emigrant/transitional and mature naive B cells from carriers of this PTPN22 risk allele contained high frequencies of autoreactive clones compared with those from non-carriers, revealing defective central and peripheral B cell tolerance checkpoints. Hence, a single PTPN22 risk allele has a dominant effect on altering autoreactive B cell counterselection before any onset of autoimmunity. In addition, gene array experiments analyzing mature naive B cells displaying PTPN22 risk allele(s) revealed that the association strength of PTPN22 for autoimmunity may be due not only to the impaired removal of autoreactive B cells but also to the upregulation of genes such as CD40, TRAF1, and IRF5, which encode proteins that promote B cell activation and have been identified as susceptibility genes associated with autoimmune diseases. These data demonstrate that early B cell tolerance defects in autoimmunity can result from specific polymorphisms and precede the onset of disease.