RESUMO
BACKGROUND: The recombination-activating gene (RAG) 1/2 proteins play a critical role in the development of T and B cells by initiating the VDJ recombination process that leads to generation of a broad T-cell receptor (TCR) and B-cell receptor repertoire. Pathogenic mutations in the RAG1/2 genes result in various forms of primary immunodeficiency, ranging from T(-)B(-) severe combined immune deficiency to delayed-onset disease with granuloma formation, autoimmunity, or both. It is not clear what contributes to such heterogeneity of phenotypes. OBJECTIVE: We sought to investigate the molecular basis for phenotypic diversity presented in patients with various RAG1 mutations. METHODS: We have developed a flow cytometry-based assay that allows analysis of RAG recombination activity based on green fluorescent protein expression and have assessed the induction of the Ighc locus rearrangements in mouse Rag1(-/-) pro-B cells reconstituted with wild-type or mutant human RAG1 (hRAG1) using deep sequencing technology. RESULTS: Here we demonstrate correlation between defective recombination activity of hRAG1 mutant proteins and severity of the clinical and immunologic phenotype and provide insights on the molecular mechanisms accounting for such phenotypic diversity. CONCLUSIONS: Using a sensitive assay to measure the RAG1 activity level of 79 mutations in a physiologic setting, we demonstrate correlation between recombination activity of RAG1 mutants and the severity of clinical presentation and show that RAG1 mutants can induce specific abnormalities of the VDJ recombination process.
Assuntos
Estudos de Associação Genética , Proteínas de Homeodomínio/genética , Imunodeficiência Combinada Severa/genética , Recombinação V(D)J , Alelos , Linfócitos B/imunologia , Linfócitos B/metabolismo , Criança , Pré-Escolar , Ordem dos Genes , Rearranjo Gênico , Proteínas de Homeodomínio/metabolismo , Humanos , Cadeias Pesadas de Imunoglobulinas/genética , Lactente , Recém-Nascido , Mutação , Fenótipo , Imunodeficiência Combinada Severa/imunologia , Imunodeficiência Combinada Severa/metabolismo , Linfócitos T/imunologia , Linfócitos T/metabolismoRESUMO
We report an 11-year-old boy with a longstanding history of recurrent pyoderma gangrenosum and abnormal wound healing who eventually developed a fatal invasive fungal infection. This article emphasizes the importance to consider leukocyte adhesion deficiency type 1 in the differential diagnosis of patients with recurrent skin ulcers.