RESUMO
Most autosomal genetic causes of childhood-onset hypogammaglobulinemia are currently not well understood. Most affected individuals are simplex cases, but both autosomal-dominant and autosomal-recessive inheritance have been described. We performed genetic linkage analysis in consanguineous families affected by hypogammaglobulinemia. Four consanguineous families with childhood-onset humoral immune deficiency and features of autoimmunity shared genotype evidence for a linkage interval on chromosome 4q. Sequencing of positional candidate genes revealed that in each family, affected individuals had a distinct homozygous mutation in LRBA (lipopolysaccharide responsive beige-like anchor protein). All LRBA mutations segregated with the disease because homozygous individuals showed hypogammaglobulinemia and autoimmunity, whereas heterozygous individuals were healthy. These mutations were absent in healthy controls. Individuals with homozygous LRBA mutations had no LRBA, had disturbed B cell development, defective in vitro B cell activation, plasmablast formation, and immunoglobulin secretion, and had low proliferative responses. We conclude that mutations in LRBA cause an immune deficiency characterized by defects in B cell activation and autophagy and by susceptibility to apoptosis, all of which are associated with a clinical phenotype of hypogammaglobulinemia and autoimmunity.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Autoimunidade/genética , Síndromes de Imunodeficiência/genética , Agamaglobulinemia/genética , Apoptose , Autofagia , Linfócitos B/citologia , Proliferação de Células , Criança , Pré-Escolar , Mapeamento Cromossômico , Feminino , Ligação Genética , Genótipo , Homozigoto , Humanos , Imunofenotipagem , Masculino , Microscopia Eletrônica de Transmissão/métodos , Modelos Genéticos , Mutação , Linhagem , FenótipoRESUMO
BACKGROUND: A subset of patients with common variable immunodeficiency (CVID) have debilitating inflammatory complications strongly associated with cytomegalovirus (CMV) infection and a hyperproliferative CMV-specific T-cell response. OBJECTIVES: We studied the T-cell response to CMV and the global effect of this virus on immune effector cell populations in patients with CVID. METHODS: Antibody staining, peptide stimulation, and proliferation assays were used to profile CMV-specific T-cell function. RESULTS: CMV infection drives the CD4/CD8 ratio inversion that is characteristic of CVID. The late effector CD8(+) T-cell subset is expanded in CMV-infected patients with CVID. This expansion is largely attributable to CMV-specific cells and correlates with inflammatory disease; within the CMV-specific population, the frequency of late effector cells correlates inversely with the frequency of cells expressing programmed death 1. Supernatants from proliferating CMV-specific CD8(+) cells from patients with inflammatory disease can confer proliferative potential on cells from patients with noninflammatory CVID and healthy subjects. Blocking experiments showed that this proliferation is mediated in part by IFN-γ and TNF-α. CONCLUSIONS: These data strengthen the association of CMV with inflammatory pathology in patients with CVID, explain some of the well-known T-cell abnormalities associated with this condition, and provide a plausible mechanism for the documented therapeutic activity of anti-TNF-α and antiviral chemotherapy in managing CVID-associated inflammatory disease.
