Distribution of killer cell immunoglobulin-like receptor genes in the mestizo population from Venezuela.

This study represents the first report on the distribution of KIR genes in 205 unrelated healthy mestizo Venezuelan individuals. Genotyping analysis showed that all KIR genes are present in this population. Frequency of inhibitory killer cell immunoglobulin-like receptors (KIRs) exceeded 0.69, except for KIR2DL2 (0.29) and 2DL5 (0.37). Activating KIRs showed low frequencies (0.11-0.29), except for KIR2DS4 (0.68). Forty-five different KIR genotypes were identified, with a predominance of three genotypes found in 50.7% of the population of which 25.9% were individuals homozygous for haplotype A. The frequencies of KIR genes reflect the ethnic admixture existing in the mestizo Venezuelan population.

Polimorfismo HLA-DQ en pacientes pediátricos con enfermedad Celíaca

La Enfermedad celíaca es una enteropatía caracterizada por malabsorción y daño epitelial del intestino delgado, del cual se han aislado células T específicas al gluten y restringidas a los heterodímeros DQ2-DQ8, sugiriendo que los alelos DQ juegan un papel clave en la patogénesis de la enfermedad por la presentación de péptidos derivados del gluten a linfocitos T de la mucosa. En nuestro estudio evaluamos el polimorfismo HLA-DQA y DQB en pacientes pediátricos con Enfermedad Celiaca. Se estudiaron 16 pacientes que acudieron al Servicio de Gastroenterología Pediátrica del Hospital "JM de los Ríos". Los polimorfismos se definieron mediante PCR-secuenciación; las asignaciones alélicas y haplotípicas se determinaron por contaje directo. En concordancia con estudios realizados en otras poblaciones, este estudio sugiere que los heterodímeros HLA-DQ2 y DQ8 son marcadores genéticos de predisposición al desarrollo de la enfermedad celíaca. Siendo este reporte el primero en el País en resaltar la presencia de los HLA en la enfermedad celíaca.

The celiac disease is an enteropathy characterized by malabsortion and epitelial damage of the small bowel, of the one which cells specific T has been isolated to gluten and restricted to the DQ2-DQ8 heterodímers, suggesting that the DQ alelles play a key role in the pathogenesis of the disease for the presentation of derived péptides from the gluten to T linfocites. In our study we evaluate the HLA-DQA and DQB polymorphism in pediatric patients with celiac Disease. 16 patients were studied from Gastroenterology service of the "Hospital de Niños JM de los Ríos". The polymorphism was defined through PCR-sequence; the assignments of alleles and haplotype were determined by direct count. Similar to other reports which suggest HLA DQ2 y DQ8 as markers in genetic predisposition in celiac disease, this study is the first in Venezuela in screened HLA in Celiac Disease.

HLA-DRB1*0402 haplotypes without DQB1*0302 in Venezuelan patients with pemphigus vulgaris.

The two basic forms of autoimmune intraepidermal blistering diseases, pemphigus vulgaris (PV) and pemphigus foliaceus (PF), affect different layers of the skin, have different symptoms and target different antigens. We have defined human leukocyte antigen (HLA)-DRB1-DQB1 alleles and haplotypes in a case-control study of 66 non-Jewish patients attending a public reference Hospital over the past 10 years. The control group consisted of 101 matched individuals tested also by medium to high-resolution polymerase chain reaction-sequence-specific oligonucleotide with primers and probes from the 12th and 13th International Histocompatibility Workshop. Patients and controls were descendants of three-generation individuals born in the country. Among the patients, 49 had PV, 50% showed predominantly mucosal involvement, 50% showed predominantly the cutaneous clinical phenotype and 17 had PF. Statistically significant HLA-DR frequency differences between patients with PV and controls were found only for DRB1*0402 and DRB1*1401 [odds ratio (OR) = 27.22, confidence interval (CI) 94.7-7.82, P= 1.1 x 10(-14) and OR = 46.56, CI 801.4-2.70 P= 7.5 x 10(-6), respectively]. Both alleles were also increased in the patients with PF compared with the controls (OR = 7.0, P= 0.038 and OR = 21.64, P= 0.009, respectively), but the significance of the difference did not resist Bonferroni correction. Haplotype analysis showed that DRB1*0402 was always present with DQB1*0302 and DRB1*1401 with DQB1*0503, but no independent effect of the DQB1*0302 in the former haplotype was evident. Our results support the hypothesis that the DRB1*0402 without DQB1*0302 is the most relevant HLA-DRB1 allele responsible for the pathogenesis of pemphigus in Venezuelan patients with PV and discard the DQB1*0302 influence observed in other populations.

Human leukocyte antigen class I and MICA haplotypes in a multicase family with Cladophialophora carrionii chromoblastomycosis.

Previous studies carried out in an endemic semiarid region northwest of Venezuela at Falcon State have shown a prevalence of 15.4/1000 of chromoblastomycosis following traumatisms with xenophile vegetation infected with Cladophialophora carrionii. We performed high-resolution DNA typing of human leukocyte antigen (HLA)-A, -B and -C and major histocompatibility complex class I chain related gene A (MICA) alleles and segregation analysis in 49 members of one extended family with 12 affected individuals, who have lived for approximately 70 years in this endemic zone. None of the alleles, haplotypes or genotypes is shared by all the patients. No deviation from the expected HLA haplotype distribution or association of chromoblastomycosis with HLA-A, -B and -C haplotypes was observed. Further, a haplotype-sharing transmission/disequilibria testing of 11 nuclear families did not give enough evidence to claim linkage (P = 0.398), suggesting that genes located in the short arm of chromosome 6 may not be relevant in the immune response toward infection with C. carrionii in this Venezuelan endemic zone. Deleted MICA alleles on HLA-B*4802 haplotypes were present among several members of the extended family, but only two of them were affected.

Use of short tandem repeats loci to study the genetic structure of several populations from Zulia State, Venezuela.

Genetic relationships between populations can be studied by comparing genotypic and allelic similarities. This investigation aims to demonstrate that selected autosomal microsatellite markers could be used to study the genetic structures of different populations living in northwest Venezuela, in Zulia State. Seven autosomal systems (CSF1PO, TPOX, TH01, vWA, D7S820, D13S317, and D5S818) were tested by PCR in a multiplex format on 688 different chromosomes from unrelated individuals living in Maracaibo, "Isla de Toas," and "San José de Heras," and from two Amerindian populations from the "Sierra de Perijá," Barí' and Yukpa. Allele frequencies, Hardy-Weinberg equilibria, genetic distances, phylogenetic trees, and ethnic admixtures were estimated. The study shows the existence of a clear genetic difference among these populations in accordance with their historic evolution. The populations of Maracaibo and "Isla de Toas" showed a triracial origin, with a large European contribution, followed by an Amerindian component and a small African component. The indigenous groups, Barí' and Yukpa, showed exclusively an Amerindian component, and "San José de Heras" showed only an African component. These results indicate that microsatellite markers are useful for molecular anthropology in a regional and worldwide context and provide important genetic information about contemporary populations of Venezuela.

Genetic variability of Apolipoprotein E in different populations from Venezuela.

The genetic variation at the Apolipoprotein E locus (APOE) is an important determinant of plasma lipids and has been implicated in various human pathological conditions. The objective of the present study was to estimate the distribution of APOE alleles in five Venezuelan communities: two Amerindian tribes (Bari and Yucpa), one Negroid population from Curiepe, one Caucasoid population from Colonia Tovar and the Mestizo urban population living in Caracas. The APOE*3 allele was the most common allele in all populations studied. However, a significant increase in the APOE*2 allele frequency in the Mestizo (18.96%) and Negroid (16.25%) populations was found. Similar to results reported in other Native American populations we have found that the APOE*2 allele is completely absent in the Bari and Yucpa Amerindians. Frequencies found in the Colonia Tovar population are in agreement with those reported in the population of Germany, indicating a high degree of relatedness. The results support the notion that the distribution of the APOE alleles shows ethnic variability.

TNF-alpha-308A allele, a possible severity risk factor of hemorrhagic manifestation in dengue fever patients.

Among the several hypothesis postulated to explain the pathogenesis of severe dengue disease, the model of immunopathogenesis is the most supported one with a likely important role played by the cascade of cytokines. This work describes single-nucleotide polymorphism of tumor necrosis factor (TNF)-alpha, interferon-gamma, interleukin (IL)-6, transforming growth factor-beta1, and IL-10 in patients with dengue virus infections and analyzes their relation with clinical manifestations of the disease. Because cytokine gene polymorphisms affect cytokine production, the significant increase of the TNF-308A allele we have observed among patients with dengue fever (DF) with hemorrhagic manifestations compared to patients with DF only indicates that the former patients are genetically predisposed to express higher levels of TNF-alpha. This finding supports studies reporting a possible association between elevated levels of circulating TNF, vascular permeability, and hemorrhage in patients with dengue hemorrhagic fever.

Is the CCR5-59029-G/G genotype a protective factor for cardiomyopathy in Chagas disease?

Investigated were two CCR5 gene polymorphisms, the CCR5 Delta 32 deletion and the pCCR5 59029 A-->G promoter point mutation, in 107 ethnically mixed Venezuelan patients serologically positive for Trypanosoma cruzi (34 asymptomatic, 38 arrhythmic, 35 cardiomyopathic). No difference in the distribution of CCR5 Delta 32 among asymptomatic and symptomatic patients was found. We have observed an increase of the 59029-G phenotype among asymptomatic compared with symptomatic chagasic patients (68% vs. 58%), in agreement with previously reported data (57% vs. 31%). This frequency difference, although not statistically significant, is more marked when the 59029-G allele is present in homozygous form. However, a similar distribution of the G/G genotype is present among asymptomatic patients and patients with heart failure. Because it has been reported that the 59029G/G genotype associates with lower CCR5 expression, 37% of our T. cruzi-infected patients with heart failure are genetically predisposed to express low levels of CCR5 on the surface of CD8(+) T cells, contrary to what would be expected if an inflammatory response is required for severe cardiac damage. If confirmed, the possible protection that might be conferred by the G/G genotype may be due to the existence of other genes in linkage disequilibria.

Colonia Tovar: the history of a semi-isolated Venezuelan population of German ancestry described by HLA class I genes.

The history of Colonia Tovar is very complex, being the home of descendants of only a small fraction of immigrants arriving to the South American continent from a specific region of Germany, with a restricted number of founders, small population size and consanguineous mating, experiencing isolation for 100 years, with later migrations, a low rate of population growth and a high mean number of children per couple. How complex is its genetic structure? Do the highly polymorphic HLA genes reflect its history and confirm the story of this population described by other genes? Several studies have been made in this population, but we describe for the first time the HLA Class I variability in the population of Colonia Tovar using PCR-SSOP. Random genetic drift, founder effect and gene flow could explain the HLA allele and haplotype frequencies observed in this population but alleles at the class I loci were insufficient to identify the German origin of the community established through history. This agrees with findings obtained testing other genetic systems (ACP, AK, ESD, G6PD, GLO, PGM, PGD, ALB, CP, HP, TF), but the HLA-typing results indicate that the original gene pool has been diluted due to gene flow from the surrounding Mestizo population.

Y-chromosome biallelic polymorphisms and Native American population structure.

It has been proposed that women had a higher migration rate than men throughout human evolutionary history. However, in a recent study of South American natives using mtDNA restriction fragment polymorphisms and Y-chromosome microsatellites we failed to detect a significant difference in estimates of migration rates between the sexes. As the high mutation rate of microsatellites might affect estimates of population structure, we now examine biallelic polymorphisms in both mtDNA and the Y-chromosome. Analyses of these markers in Amerinds from North, Central and South America agree with our previous findings in not supporting a higher migration rate for women in these populations. Furthermore, they underline the importance of genetic drift in the evolution of Amerinds and suggest the existence of a North to South gradient of increasing drift in the Americas.

Preeclampsia: a multifactorial disease resulting from the interaction of the feto-maternal HLA genotype and HCMV infection.

PROBLEM: To clarify the possible influence of human leukocyte antigen (HLA) mother-child genotypes and human cytomegalo virus (HCMV) presence on the development of preeclampsia. METHODS OF STUDY: One hundred and four DNA samples from mothers with preeclampsia, mothers with a normal history of pregnancies and their neonates were tested by polymerase chain reaction-sequence specific oligonucleotide probes (PCR-SSOP) for HLA-A, -G, -DRB1, -DQA1, -DQB1 alleles. The HCMV sequences were analyzed using a PCR-SSOP method and the four primers described by Chou (Chou S: J Clin Microb 1992; 30:2307-2310). RESULTS: Compared with their respective controls, a significant increase of DRB1*07 among neonates (P(c) = 0.05) and of DRB1*07 and/or DRB1*06 among pre-eclamptic mothers (P(c) = 0.003, RR = 8,5) was found. When HCMV sequences were detected in pre-eclamptic mothers carrying those phenotypes the RR increased up to 40. Furthermore, the fetal inheritance of a maternal HLA-G*0104 increased the risk for the appearance of the disease (RR = 30; P = 0.025). CONCLUSION: The results suggest that the presence of alleles HLA-G*0104, DRB1*07/06, HCMV sequences and the fetal inheritance of maternal G*0104, should be considered as conditioning factors for the development of preeclampsia.

Analysis of the T-cell receptor beta-chain variable-region (Vbeta) repertoire in chronic human Chagas' disease.

Previous studies have shown that infection with the protozoan Trypanosoma cruzi (Chagas' disease) is associated with genetic components [human leukocyte antigen (HLA) genes and T-cell receptor (TCR) genes]. We studied the TCR Vbeta repertoire of peripheral blood lymphocytes of 23 unrelated serologically positive subjects using reverse transcriptase-polymerase chain reaction (RT-PCR). The patients, previously tested for HLA genotypes, were clinically classified as asymptomatic, arrhythmic and cardiopathic patients. Statistical analysis showed the significant increment of the Vbeta7 family in chagasics with arrhythmia compared with asymptomatic and cardiopathic patients, indicating that the frequency of this family is variable in different clinical forms of the disease and possibly that these T cells might be a marker of the progression of Chagas' disease. Based on the calculation of a Delta score the order of variability in the TCR repertoire was: patients with heart failure > asymptomatic > arrhythmic patients. The major histocompatibility complex (MHC) of the individual may influence the use of particular V genes in T-cell response to foreign antigens. We found a significant increase of the Vbeta7 family in arrhythmic patients who were DRB1*01 DQB1*0501 DPB1*0401, a marker associated with susceptibility to cardiac damage in Chagas' disease. If confirmed by further studies in a larger cohort, a possible association between the TCR Vbeta repertoire and the MHC haplotype of chagasic patients could be postulated.

Extended HLA haplotypes in a Carib Amerindian population: the Yucpa of the Perija Range.

Eleven MHC loci haplotypes have been defined among a Carib speaking Amerindian population; the Yucpa, inhabiting the northern section of the Perija Range, on the limits between Colombia and Venezuela. This tribe has been known with the name of "Motilones mansos" and is located close to the Chibcha-Paeze speaking Bari or "Motilones bravos." Seventy-three full blooded Yucpa living at the villages of Aroy, Marewa, and Peraya, were selected using a genealogy previously collected by an anthropologist and tested for Bf-C4AB complement allotypes and by serology, high resolution PCR-SSO and SBT typing for HLA class 1 and class 2 alleles. Combinations of 6 HLA-A, 6 HLA-B, 5 HLA-C, 1 Bf, 3 C4AB, 3 DQA1, 3DQB1 and 2 DPA1 and 2 DPB1 alleles present in this population originate 17 different haplotypes, 3 of which represent 63% of the haplotypic constitution of the tribe. The presence of 13 individuals homozygous for 11-loci haplotypes corroborates the existence of the following allelic combinations: DRB1*0411 DQA1*03011 DQB1*0302 DPA1*01 DPB1*0402 with HLA-A*6801 C*0702 B*3909 BfS C4 32 (f = 0.3372) or with A*0204 C*0702 B*3905 (f = 0.1977) and a third haplotype which differs only in DRB1*0403 and A*2402 (f = 0.0930). The results demonstrate the isolation of the tribe and the existence of high frequencies of a reduced number of "Amerindian" ancestral and novel class 1 and class 2 alleles (B*1522, DRB1*0807) with significant linkage disequilibria. These results will be useful to test the hypothesis that differentiation of Amerindian tribal groups will have to rely on haplotypes and micropolymorphism rather than allelic lineage frequencies due to the uniformity shown thus far by the putative descendants of the original Paleo-Indians.

HLA-C(*)03 is a risk factor for cardiomyopathy in Chagas disease.

Previous studies have shown the effect of class 1 as detected by serology or class 2 HLA genes by oligotyping upon susceptibility or resistance to the cardiomyopathy that develops in approximately one third of the Trypanosoma cruzi chronically infected patients. Low and intermediate resolution DNA typing of class 1 alleles was performed in a sample of 113 serologically positive individuals with and without cardiomyopathy. A polymerase chain reaction-sequence-specific oligonucleotide probe method using primers and probes from the British Society of Histocompatibility and Immunogenetics as modified for the VII Latin American Histocompatibility Workshop by D. Middleton, and LiPA kits from Innogenetics were used. Several alleles (A(*)11, A(*)31, B(*)15, B(*)35, B(*)45, B(*)49, B(*)51, and C(*)03) showed increased frequencies among patients with cardiac damage versus the asymptomatic group, but only the last one remained significant after correction of the p value (OR = 5.8, p(c) = 0.03). HLA-C(*)03 showed linkage disequilibrium with B(*)40 and B(*)15 and although both haplotypes were increased in cardiopathic patients compared with asymptomatic individuals, the difference is not significant. These results suggest that the HLA-C*03 allele could confer susceptibility to the development of cardiomyopathy among Venezuelan T. cruzi seropositive individuals and contrast with the protective effect conferred by the HLA B40 Cw3 haplotype among Chilean chagasic patients. Further studies will be needed to confirm the role of this allele on the cardiomyopathy of Chagas disease.

HLA class II DRB1, DQB1, DPB1 polymorphism and cardiomyopathy due to Trypanosoma cruzi chronic infection.

Trypanosomiasis is an important cause of cardiomyopathy in endemic rural areas of Latin America. Previous studies have suggested participation of HLA molecules in the immune response regulation of T. cruzi infection, and association of HLA antigens with heart damage. One hundred and eleven unrelated T. cruzi antigen-seropositive individuals were tested for HLA class II alleles by the polymerase chain reaction and sequence specific oligonucleotide (PCR-SSO) method. Patients were classified in 3 groups according to clinical and electrocardiographic characteristics: asymptomatics (group A), with arrhythmia (group B), and with overt congestive heart failure (group C). Statistical analysis confirmed the significant increment of the DRB1*01 DQB1*0501 haplotype (p = 0.03) previously reported by our laboratory in patients with cardiomyopathy. The DPB1*0401 allele frequency is also significantly increased in patients with heart disease (groups B + C) (p = 0.009) while DPB1*0101 frequency is higher among the asymptomatic group (p = 0.04) compared with individuals of group C. The DPB1*0401 allele in homozygous form or in combination with allele DPB1*2301 or 3901, was found present more often in patients of groups B and C. Thus, the combination of two of these three alleles, sharing specific sequence motifs in positions 8, 9, 76, and 84-87 confers a relative risk of 6.55 to develop cardiomyopathy in seropositive patients (p = 0.041). Furthermore, 32% of the cardiomyopathics have either DRB1*01 DQB1*0501 and/or DPB1*0401/*0401, 0401/*2301, or* 0401/*3901 compared with 9% of the seropositive asymptomatics (OR = 5.0; p = 0.006).

Genetic diversity of two African and sixteen South American populations determined on the basis of six hypervariable loci.

A total of 582 individuals (1,164 chromosomes) from two African, eight African-derived South American, five South American Amerindian, and three Brazilian urban populations were studied at four variable number of tandem repeat (VNTR) and two short tandem repeat (STR) hypervariable loci. These two sets of loci did not show distinct allele profiles, which might be expected if different processes promoted their molecular differentiation. The two African groups showed little difference between them, and their intrapopulational variation was similar to those obtained in the African-derived South American communities. The latter showed different degrees of interpopulation variability, despite the fact that they presented almost identical average degrees of non-African admixture. The F(ST) single locus estimates differed in the five sets of populations, probably due to genetic drift, indicating the need to consider population structure in the evaluation of their total variability. A high interpopulational diversity was found among Amerindian populations in relation to Brazilian African-derived isolated communities. This is probably a consequence of the differences in the patterns of gene flow and genetic drift that each of these semi-isolated groups experienced.

Immunogenetics of atopic asthma: association of DRB1*1101 DQA1*0501 DQB1*0301 haplotype with Dermatophagoides spp.-sensitive asthma in a sample of the Venezuelan population.

BACKGROUND: Genes linked to the major histocompatibility complex (MHC), have been implicated in atopic asthma. Asthma is highly prevalent in the Venezuelan population (estimated at 20%) and genetic markers are needed to identify populations at risk and plan intervention strategies. OBJECTIVE: To study the influence of the MHC class I and class II genes in the susceptibility to atopic asthma. METHODS: MHC-class I HLA-A, -C, -B and MHC-class II HLA-DR, -DQ, -DP gene haplotype frequencies were determined in 135 Venezuelan mestizos, 71 belong to 20 atopic asthmatic families and 64 unrelated controls. The index cases were 20 atopic asthmatics with positive skin-prick tests and specific serum immunoglobulin E (IgE) for Dermatophagoides pteronyssinus (Der p) and Dermatophagoides farinae (Der f). To ascertain the genes associated with susceptibility to atopy and/or asthma, two control groups were studied, 41 non-atopic subjects with skin-prick negative test, and undetectable levels of specific IgE and 23 non-asthmatic atopic subjects with detectable specific IgE to Der p and Der f. A linkage analysis was performed in those families with two or more atopic siblings (with or without asthma). RESULTS: MHC-class I genes analysis showed that HLA-Cw7 was absent in the asthmatic patients studied, whereas the frequency of this allele was 14.3% in non-atopic controls (P = 0.0 17, PC = 0.19) and 20.8% in the atopic controls (P = 0.0066, PC = 0.07). MHC-class II gene analysis showed a significant increase of the HLA-DRB1*11 in the asthmatic patients compared with non-atopic controls (allele frequencies of 25.6 vs 4.4% P = 0.0017, PC = 0.02). There were no significant differences among asthmatic and atopic controls in the frequency of HLA-DRB1*11 (25.6 vs 17.4%). In contrast, the HLA-DRB1*1101+ haplotypes were significantly higher in asthmatics compared with atopic and non-atopic controls (19.6% vs 2.2% vs 2.3%, PC<0.05). The HLA-DRB1*1101, DQA1*0501, DQB1*0301 haplotype was found significantly increased in the patients vs non-atopic controls (15.4 vs 1.1%, PC< 0.01). The serum levels of specific IgE were detectable in both atopic asthmatics and atopic controls; however, it was higher in atopic asthmatics vs atopic controls Der p (median, 58.7 vs 2.7 kU/L, P<0.001) and Der f (median, 46.9 vs 2.7 kU/L, P<0.001). No linkage between MHC genes and mite-atopy could be documented on informative families with two or more atopic siblings. CONCLUSIONS: We have identified an association between the haplotype HLA-DRB1*1101, DQA1*0501, DQB1*0301 and atopic asthma that confers susceptibility to develop mite-sensitive asthma to atopics (relative risk, RR 8.2), and to non-atopic controls (RR = 15.8) that carry this haplotype. Conversely, the allele HLA-Cw7 was absent in the asthmatics studied and had higher frequencies in the atopic (RR = 0.05) and non-atopic (RR = 0.08) controls. Thus, it may have a protective role for developing atopic asthma in the population studied.

Fetal natural killer cell function is suppressed.

Previous studies have reported reduced natural killer (NK) cell activity in cord blood (CB) compared with adult blood mononuclear cell populations. Using a non-radioactive killing assay, we have verified these findings suggesting that either the fetal NK cell function is suppressed or that these cells are functionally immature. We have shown that CB NK cells are functional, since activating them with cytokines known to activate adult NK cells [interleukin-2 (IL-2), IL-12 and IL-15] increased activation. However, resting the cells, which enhanced adult NK cell activity (P < 0.01), had no effect on fetal NK cells (P = 0.2). These results suggested that fetal NK cells have the capacity to kill, but this is suppressed in vitro. This hypothesis was strengthened by our observation that eight of nine CB mononuclear cell populations had their NK activity restored by freeze-thawing, whereas four of five adult peripheral blood mononuclear cells had a reduced killing ability on freeze-thawing. Freeze-thawing removes a population of cells that suppresses CB NK cell function. To determine which was the case we performed extensive phenotypic analysis of the CB populations pre- and post-freezing and found that the percentage of the CD3- CD56+ population within CB increased significantly (P < 0.0005 by paired t-test) with freezing, whereas freeze-thawing had no effect on this population within a normal adult peripheral blood mononuclear cell population. Our data suggest that within CB there is a population of cells, as yet undefined, which may be inhibiting NK cell function. This report therefore shows clear differences between NK cells within the adult periphery and in CB, and may lead to a better understanding of events occurring in vivo.

Characterization of the HLA class I genotypes of a Venezuelan Amerindian group by molecular methods.

We have characterized the HLA class I genotypes of the Yucpa, a tribe of Venezuelan Amerindians, using molecular methods. The study was carried out on DNA extracted from unrelated individuals using low resolution ARMS-SSP typing with sequence-specific primers, high resolution typing using reference strand conformation analysis (RSCA), and for some samples sequence-based typing (SBT). The following class I alleles were found to be present in this tribe: for the HLA-A locus A*0204, A*0212, A*0213, A*2402, A*3101 and A*6801; for the B locus B*1522, B*3512, B*3905, B*3909, B*4004 and B*52012, and for C locus Cw*0102, Cw*0302/ 4, Cw*0401, Cw*0702 and Cw*1503. This is the first time these alleles have been described in this group, although all of them have previously been reported as being present in other Amerindian tribes. The study confirmed the high frequency of HLA-B39 which was previously observed in serological analysis of this tribe, and indicated that two different B*39 alleles were present in this population. The identification of the class I alleles by molecular methods for this ethnic group confirms the restricted polymorphism of the MHC molecules previously obtained by serology and has allowed a more accurate definition of the different alleles present in this population.

Influence of the HLA class II polymorphism in chronic Chagas' disease.

Chagas' disease or American trypanosomiasis due to Trypanosoma cruzi has existed at least since the time of the Inca empire and contributes significantly to cardiovascular morbidity and mortality in several countries of this continent. Due to the fundamental role of human class II molecules polymorphic residues in the control of the immune response, a study was designed to define by DNA typing HLA class II alleles in a sample of 67 serologically positive individuals with and without cardiomyopathy and in 156 healthy controls of similar ethnic origin. Genomic DNA extraction, PCR amplification of the HLA-DRB1 and DQB1 second exon regions and hybridization to labelled specific probes were carried out following the 11th International Histocompatibility Workshop reference protocol. Comparison of DRB1 and DQB1 allele frequencies among the patients and control subjects showed a decreased frequency of DRB1*14 and DQB1*0303 in the patients, suggesting independent protective effects to the chronic infection in this population. Allele frequencies comparison between patients with and without cardiomyopathy showed a higher frequency of DRB1*01, DRB1*08 and DQB1*0501 and a decreased frequency of DRB1*1501 in the patients with arrhythmia and congestive heart failure. The results suggest that HLA Class II genes may be associated with the development of a chronic infection and with heart damage in Chagas' disease.