RESUMO
Cell-mediated immunity requires costimulatory activity to initiate or inhibit antigen-specific T-cell responses. CTLA-4 is an inhibitory receptor expressed by activated and regulatory T cells. The single nucleotide polymorphism (SNP) +49 A/G of the CTLA-4 gene alters intracellular distribution of CTLA-4, interleukin-2 production, and, as a consequence, T-cell proliferation. The aim of this study was to analyze the only coding SNP CTLA-4 +49 A/G polymorphism in patients with either infectious (Chagas's, Dengue, and American cutaneous leishmaniasis) or autoimmune diseases (myasthenia gravis, pemphigus, and psoriasis). No statistically significant differences were reported when all patients of each disease group were compared with healthy individuals. However, the +49 G/G genotype was moderately increased in pemphigus and myasthenia gravis. Patients with diffuse cutaneous leishmaniasis (DCL) exhibited an increased frequency of the A/G +49 genotype compared with patients with localized cutaneous leishmaniasis (LCL; p = 0.009; odds ratio [OR] = 4.25; 95% confidence interval [CI] = 1.245-14.501) and intermediate cutaneous leishmaniasis (ICL; p = 0.027; OR = 4.44; 95% CI = 1.273-15.516), indicating that the heterozygous genotype, associated with overactivation of T-cell proliferation, could confer susceptibility to the development of the more severe clinical form of cutaneous leishmaniasis. The A/A +49 genotype was increased in LCL patients compared with DCL patients (p = 0.019; OR = 0.25; 95% CI = 0.067-0.953), indicating that this genotype, which has been associated with normal proliferation of T cells, could confer protection to the development of DCL. The results indicate that the polymorphism of CTLA-4 is an important genetic factor associated with risk or protection for the development of diffuse cutaneous leishmaniasis and has influence in the pathogenesis of autoimmune diseases. However, other closely linked candidate genes in linkage disequilibrium with CTLA4, such as CD28 and ICOS, could be associated with the development of autoimmune and infectious disease.
Assuntos
Antígenos CD/genética , Doenças Autoimunes/genética , Doenças Transmissíveis/genética , Polimorfismo de Nucleotídeo Único , Alelos , Antígeno CTLA-4 , Doença de Chagas/genética , Dengue/genética , Frequência do Gene , Predisposição Genética para Doença , Genótipo , Humanos , Leishmaniose Cutânea/genética , Miastenia Gravis/genética , Pênfigo/genética , Psoríase/genética , Fatores de RiscoRESUMO
Interaction between killer cell immunoglobulin-like receptors (KIR) and cognate HLA class I ligands influences the innate and adaptive immune response to infection. The KIR family varies in gene content and allelic polymorphism, thereby, distinguishing individuals and populations. KIR gene content was determined for 230 individuals from three Amerindian tribes from Venezuela: the Yucpa, Bari and Warao. Gene-content haplotypes could be assigned to 212 individuals (92%) because only five different haplotypes were present-group A and four group B. Six different haplotype combinations accounted for >80% of individuals. Each tribe has distinctive genotype frequencies. Despite few haplotypes, all 14 KIR genes are at high frequency in the three tribes, with the exception of 2DS3. Each population has an even frequency of group A and B haplotypes. Allele-level analysis of 3DL1/S1 distinguished five group A haplotypes and six group B haplotypes. The high frequency and divergence of the KIR haplotypes in the Amerindian tribes provide greater KIR diversity than is present in many larger populations. An extreme case being the Yucpa, for whom two gene-content haplotypes account for >90% of the population. These comprise the group A haplotype and a group B haplotype containing all the KIR genes, except 2DS3, that typify the group B haplotypes. Here is clear evidence for balancing selection on the KIR system and the biological importance of both A and B haplotypes for the survival of human populations.
Assuntos
Variação Genética , Indígenas Sul-Americanos/genética , Receptores Imunológicos/genética , Frequência do Gene , Haplótipos/genética , Humanos , Receptores KIR , Receptores KIR3DL1 , Venezuela/etnologiaRESUMO
POPULATIONS: Whole blood samples from 74 unrelated healthy individuals were collected. The donors' sample included Venezuelan mestizos from various regions of the country, but mostly from the resident population of Caracas City. A Venezuelan mestizo is the offspring of a mating between a native Venezuelan and a person born in Europe, mainly in Spain.
Assuntos
Frequência do Gene , Genética Populacional , Antígenos HLA/genética , Polimorfismo Genético , Sequências de Repetição em Tandem , Impressões Digitais de DNA , Humanos , Reação em Cadeia da Polimerase , VenezuelaRESUMO
Three different Venezuelan Amerindian tribes were studied for human leukocyte antigen (HLA)-DPA1 and DPB1 allelic variability using polymerase chain reaction-sequence-specific oligonucleotide probes (PCR-SSOP) and sequence-based typing in a selected group of samples. These tribes are geographically (two from the Perija Mountain range and one from the Orinoco Delta) and linguistically distinct: the Bari (from Campo Rosario and Saymaidoyi villages) and the Warao have been classified within the Chibcha linguistic family, whereas the Yucpa (from the Aroy, Marewa, and Peraya villages) are Carib speaking. Venezuelan Indians, like other Native American tribes, show a markedly reduced number of different HLA-DP alleles (range, 2-7) and haplotypes (range, 4-11) in comparison with neighboring Venezuelan mestizo and other non-Indian populations. Some HLA-DPB1 (*0402 and *1401) alleles characteristic for all Amerindian tribes are present also in these populations. Despite general similarities, each tribe and, in some cases, some subtribes show their own pattern of allele and haplotype distribution apparently more as a result of linguistic than to geographic variation.
Assuntos
Antígenos HLA-DP/genética , Alelos , Frequência do Gene , Variação Genética , Cadeias alfa de HLA-DP , Cadeias beta de HLA-DP , Haplótipos , Humanos , Indígenas Sul-Americanos/classificação , Indígenas Sul-Americanos/genética , Linguística , Filogenia , Polimorfismo Genético , VenezuelaRESUMO
Oligotyping performed among ethnically mixed Venezuelan patients with myasthenia gravis (MG) and controls has revealed positive associations of HLA class I A*31, B*08, B*39, B*40, C*15, C*17, and class II DRB1*09 and negative associations of DQB1*06 and DQA1*02 with the disease. Sequential removal of human leukocyte antigen B (HLA-B) alleles when relative predispositional effects (RPEs) were looked for demonstrated that B*08 is the allele group with the largest contribution in the overall MG patients followed by B*39 and B*40. Several specificities (A*31, B*08, C*17, DRB1*03, DQA1*05, and DQB1*02) indicated increased frequencies among patients with thymic hyperplasia versus patients without hyperplasia or controls. Tests to identify alleles with the strongest association to MG in our patients detected DRB1*13 and B*38 as possible predisposing secondarily associated alleles in patients with hyperplasia. The associations observed disappear after Bonferoni correction of probability values and have been described in patients of Caucasian and/or Oriental ethnic background. Thus, our results reflect the heterogeneity of our population and of the patients tested and suggest a limited influence of several HLA genes in this heterogeneous disease or that these might be only markers of nearby non-HLA genes responsible for the susceptibility or resistance effect.
Assuntos
Doenças Autoimunes/genética , Genes MHC da Classe II , Genes MHC Classe I , Miastenia Gravis/genética , Polimorfismo Genético , Adulto , Alelos , Doenças Autoimunes/epidemiologia , Etnicidade/genética , Feminino , Frequência do Gene , Predisposição Genética para Doença , Humanos , Hiperplasia , Masculino , Pessoa de Meia-Idade , Miastenia Gravis/epidemiologia , Miastenia Gravis/patologia , Fenótipo , Timoma/complicações , Timoma/epidemiologia , Timoma/genética , Timo/patologia , Neoplasias do Timo/complicações , Neoplasias do Timo/epidemiologia , Neoplasias do Timo/genética , Venezuela/epidemiologiaRESUMO
To scrutinize the male ancestry of extant Native American populations, we examined eight biallelic and six microsatellite polymorphisms from the nonrecombining portion of the Y chromosome, in 438 individuals from 24 Native American populations (1 Na Dené and 23 South Amerinds) and in 404 Mongolians. One of the biallelic markers typed is a recently identified mutation (M242) characterizing a novel founder Native American haplogroup. The distribution, relatedness, and diversity of Y lineages in Native Americans indicate a differentiated male ancestry for populations from North and South America, strongly supporting a diverse demographic history for populations from these areas. These data are consistent with the occurrence of two major male migrations from southern/central Siberia to the Americas (with the second migration being restricted to North America) and a shared ancestry in central Asia for some of the initial migrants to Europe and the Americas. The microsatellite diversity and distribution of a Y lineage specific to South America (Q-M19) indicates that certain Amerind populations have been isolated since the initial colonization of the region, suggesting an early onset for tribalization of Native Americans. Age estimates based on Y-chromosome microsatellite diversity place the initial settlement of the American continent at approximately 14,000 years ago, in relative agreement with the age of well-established archaeological evidence.
Assuntos
Povo Asiático/genética , Cromossomos Humanos Y , Emigração e Imigração/história , Genética Populacional/história , Indígenas Norte-Americanos/genética , Indígenas Sul-Americanos/genética , Povo Asiático/história , Canadá , Marcadores Genéticos , Haplótipos , História Antiga , Humanos , Indígenas Norte-Americanos/história , Indígenas Sul-Americanos/história , Masculino , Repetições de Microssatélites , Polimorfismo Genético , Sibéria , América do SulRESUMO
Los avances en la genética y epidemiología de la diabetes mellitus tipo I, de etiología auto-inmune y el descubrimiento de marcadores inmuno-genéticos están dilucidando la fisiología del texto proceso de destrucción de las células beta del páncreas en la fase pre-diabética que finalmente conducen a la aparición de la diabetes en su forma clínica clásica. Sólo ha sido en los últimos años que estas nuevas herramientas diagnósticas han ayudado a identificar a los individuos de alto riesgo susceptibles de desarrollar diabetes en las diferentes poblaciones mundiales, con posibilidades de tratamiento preventivos en el futuro. Nosotros, en Venezuela, hemos iniciado el estudio de nuestra población pediátrica con diabetes mellitus tipo I, encontrando que la mayoría tienen el haplotipo HLA-DR3 o DR4, en particular la asociación de HLA-DR3 con DQW2 y HLA-DR4 con DQW8. También los estudios de ADN reflejaron una meyor susceptibilidad con la ausencia de ácido aspártico en la posición 57 en la cadena de DQ beta y con la presencia de arginina en la posición 52 de la cadena DQ alfa. El marcador inmunológico más importante fue la presencia de anticuerpos anti-pancreáticos (PICA) en un 56 por ciento de los pacientes, mientras anticuerpos anti insulina (AAI) se vieron en un 8 por ciento. Sólo 11 por ciento de los familiares de 1er grado tenían antecedentes de diabetes tipo I, más de la mitad presentó alguna virosis previas al comienzo y los picos más altos de incidencia fueron en los meses de febrero a marzo y agosto a octubre
Assuntos
Humanos , Masculino , Feminino , Adolescente , Diabetes Mellitus Tipo 1/epidemiologia , Marcadores Genéticos/imunologiaRESUMO
En Venezuela no han sido reportados previamente los marcadores inmunológicos y genéticos en niños con Diabetes Mellitus tipo I durante el debut de la enfermedad. Nosotros tuvimos la oportunidad de estudiar a 27 niños recién diagnosticados con Diabetes Mellitus tipo I, con una edad promedio de 9.4+/- 3.2 años (Rango 1.3-14.9), 11 hembras y 16 varones. Ochenta y nueve por ciento tenían una historia familiar de Diabetes Mellitus (26 por ciento tipo I) 56.7 por ciento habían presentado una infección respiratoria superior previo al diagnóstico y 12.7 por ciento habían padecido de parotiditis o varicela. El pico de incidencia de la enfermedad fue durante los meses de febrero y octubre. Ochenta y nueve por ciento (24 pacientes) tenían HLD-DR3 y/o DR4 versus 37 por ciento observado en la población venezolana general; 86.1 por ciento (23 pacientes) fueron HLA-DQW2 y/o HLA DQS. Anticuerpos anti-islotes (ICA) fueron positivos en 37 por ciento (10 pacientes) y 4 de los mismos presentaron la prueba de fijación de complemento (CF/ICA) positiva. Tres pacientes presentaron anticuerpos anti-insulinicos. Solo 1 de 9 hermanos HLA idénticos al propósito presentó ICA positivo y CF/ICA positivo, y ésta niña desarrolló diabetes tipo I posteriormente. Se detectaron títulos de anticuerpos anti-virales significativamente positivos para citomegalovirus en 11 pacientes (40.7 por ciento); y títulos positivos para sarampión, parotiditis, herpes y varicela en un menor número de casos. No encontramos serotipos positivos a Coxsackie y Rubéola. Estos resultados confirman que la mayoría de nuestros diebéticos tipo I tiene HLA-DR3 oDR4 y que los fenotipos heterozigotos DR3/DR4 están significativamente aumentados en esta población. También podemos concluir que los haplotipos DR3DQW2 y DR4DQWS8 están asociados con un alto riesgo a desarrollar Diabetes Mellitus tipo I en nuestra población venezolana de origen étnico mixto