RESUMO
Familial hemophagocytic lymphohistiocytosis (FHL) is a rare, rapidly fatal, autosomal recessive immune disorder characterized by uncontrolled activation of T cells and macrophages and overproduction of inflammatory cytokines. Linkage analyses indicate that FHL is genetically heterogeneous and linked to 9q21.3-22, 10q21-22, or another as yet undefined locus. Sequencing of the coding regions of the perforin gene of eight unrelated 10q21-22-linked FHL patients revealed homozygous nonsense mutations in four patients and missense mutations in the other four patients. Cultured lymphocytes from patients had defective cytotoxic activity, and immunostaining revealed little or no perforin in the granules. Thus, defects in perforin are responsible for 10q21-22-linked FHL. Perforin-based effector systems are, therefore, involved not only in the lysis of abnormal cells but also in the down-regulation of cellular immune activation.
Assuntos
Cromossomos Humanos Par 10/genética , Histiocitose de Células não Langerhans/genética , Glicoproteínas de Membrana/genética , Células Apresentadoras de Antígenos/imunologia , Morte Celular , Linhagem Celular , Células Cultivadas , Mapeamento Cromossômico , Códon de Terminação , Grânulos Citoplasmáticos/química , Citotoxicidade Imunológica , Mutação da Fase de Leitura , Ligação Genética , Granzimas , Heterozigoto , Histiocitose de Células não Langerhans/imunologia , Humanos , Ativação Linfocitária , Glicoproteínas de Membrana/análise , Glicoproteínas de Membrana/fisiologia , Mutação de Sentido Incorreto , Perforina , Mutação Puntual , Proteínas Citotóxicas Formadoras de Poros , Serina Endopeptidases/análise , Linfócitos T Citotóxicos/química , Linfócitos T Citotóxicos/imunologiaRESUMO
OBJECTIVE: Genetic oxidation polymorphisms of debrisoquine (CYP2D6) and proguanil (CYP2C19) were studied in unrelated healthy South Pacific Polynesian volunteers recruited in the South Island of New Zealand. METHODS: Phenotyping for CYP2D6 and CYP2C19 activities was determined using debrisoquine and proguanil, respectively, as probe drugs by measuring the urinary metabolic ratio of parent drug and its metabolite. RESULTS: Of 100 Polynesian subjects phenotyped, the metabolic ratio of debrisoquine ranged from 0.01 to 9.94. Therefore, all South Pacific Polynesians were classified as extensive metabolizers of debrisoquine according to previously established criteria of the antimode. The prevalence of poor metabolizers of debrisoquine (CYP2D6) in this Polynesian population is 0% (95% confidence interval of 0-3.6%). Oxidation polymorphism of CYP2C19 using proguanil as a probe was also studied in 59 Polynesian volunteers. The frequency distribution of the proguanil/cycloguanil ratio was bimodal. The proguanil/cycloguanil ratios for these subjects ranged from 0.09 to 34.4. Using a recommended proguanil/cycloguanil ratio cut-off point of 10 established in Caucasian populations, eight Polynesian subjects were identified as poor metabolizers of proguanil (CYP2C19), which corresponds to a poor metabolizer phenotype frequency of 13.6% (a 95% confidence interval of 5.9-24.6%). CONCLUSION: The incidence of poor metabolizer phenotypes for debrisoquine (CYP2D6) in South Pacific Polynesians appears to lower than in Caucasian populations, while the prevalence of poor metabolizers for proguanil (CYP2C19) in this ethnic population is higher. The frequencies of the poor metabolizer phenotype for debrisoquine and also for proguanil in South Pacific Polynesians are similar to those reported in Asian populations.