RESUMO
Patients with a combined immunodeficiency characterized by normal numbers but impaired function of T and B cells had a homozygous p.Tyr20His substitution in transferrin receptor 1 (TfR1), encoded by TFRC. The substitution disrupts the TfR1 internalization motif, resulting in defective receptor endocytosis and markedly increased TfR1 expression on the cell surface. Iron citrate rescued the lymphocyte defects, and expression of wild-type but not mutant TfR1 rescued impaired transferrin uptake in patient-derived fibroblasts. Tfrc(Y20H/Y20H) mice recapitulated the immunological defects of patients. Despite the critical role of TfR1 in erythrocyte development and function, patients had only mild anemia and only slightly increased TfR1 expression in erythroid precursors. We show that STEAP3, a metalloreductase expressed in erythroblasts, associates with TfR1 and partially rescues transferrin uptake in patient-derived fibroblasts, suggesting that STEAP3 may provide an accessory TfR1 endocytosis signal that spares patients from severe anemia. These findings demonstrate the importance of TfR1 in adaptive immunity.
Assuntos
Antígenos CD/genética , Antígenos CD/imunologia , Síndromes de Imunodeficiência/genética , Mutação de Sentido Incorreto , Receptores da Transferrina/genética , Receptores da Transferrina/imunologia , Imunidade Adaptativa/genética , Anemia/genética , Animais , Antígenos CD/metabolismo , Linfócitos B/imunologia , Linfócitos B/metabolismo , Proteínas de Ciclo Celular , Células Cultivadas , Endocitose , Feminino , Fibroblastos/fisiologia , Humanos , Masculino , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Proteínas Oncogênicas/genética , Proteínas Oncogênicas/metabolismo , Oxirredutases , Linhagem , Receptores da Transferrina/metabolismoRESUMO
BACKGROUND: Primary antibody deficiency, the most common primary immunodeficiency disorder, represents a heterogeneous spectrum of conditions caused by a defect in any critical stage of B cell development and is characterized by impaired production of normal amounts of antigen-specific antibodies. OBJECTIVE: This retrospective study aimed at description and analysis of demographic, clinical, immunological features and complications of subjects diagnosed with primary antibody deficiency at a referral center in Jordan. METHODS: The medical records of pediatric patients who were diagnosed as primary antibody deficiency (PAD) during the period from January 2006 to June 2013 were reviewed. Patients were diagnosed as PADs based on the Pan-American Group for Immunodeficiency (PAGID) and the European Society for Immunodeficiency (ESID) diagnostic criteria. RESULTS: A total number of 53 patients with PAD were identified; 37(70%) males and 16(30%) females, 16(30%) patients with congenital agammaglobulinemia, 16(30%) patients with common variable immunodeficiency, 4(7.5%) patients with IgG subclass deficiency, 10(19%) cases with transient hypogammaglobulinemia of infancy and 7(13.5%) patients as undefined PAD. The most common infection among patients was pneumonia (62%); followed by suppurative otitis media in 49% of patients. Cytopenia was the most noted autoimmune association and was found at prevalence of 22 %, other autoimmune associations (17%) including inflammatory arthritis, discoid lupus, inflammatory bowel disease, vasculitis and celiac disease. The prevalence of long-term complications was 58%, the most frequent ones were; stunted growth in 13%, bronchiectasis and lymphoproliferation in 11% for each. CONCLUSIONS: Our results indicated that congenital agammaglobulinemia and common variable immunodeficiency are the most frequent primary antibody deficiency in our patients. The awareness of families, general population as well as primary health physicians is crucial in the establishment of early diagnosis and prompt commencement of appropriate therapy for PADs.