Frequencies of HLA-A and HLA-B alleles in a Mexico City mestizo sample

Association of HLA-DR3 and HLA-DR4 with Sinonasal Polyposis in Mexican Mestizos

OBJECTIVE: The pathogenesis of sinonasal polyposis (SNP) is not clear; it has been suggested that it is polygenic and multifactorial. The major histocompatibility complex is a useful tool to predict genetic susceptibility to diseases, especially to autoimmune diseases. Since such susceptibility is influenced by ethnicity, it is necessary to have a wide knowledge of the structure of the population to which the patient belongs. The purpose of the study was to determine the association of HLA-DRB1 alleles with sinonasal polyposis in the Mexican Mestizo population.

STUDY DESIGN: We studied the HLA-DR alleles in 34 adult Mexican Mestizo patients with SNP and compared them to those present in 99 healthy controls.

METHODS: Genomic DNA from mononuclear cells was obtained by using the “salting out” technique and high-resolution DNA typing of the HLA-DRB1 alleles was performed after PCR amplification.

RESULTS: We found a statistically significant increased frequency of the HLA-DRB1∗03 allele ( P = 0.03, odds ratio [OR] = 2.9, 95% confidence interval [CI]: 1.0–7.8) and of the HLA-DRB1∗04 allele ( P = 0.009, OR = 2.2, 95% CI: 1.2–4.2) in patients with SNP as compared to controls, and a statistically significant decreased frequency of the HLA-DRB1∗08 allele ( P = 0.01, OR = 0.2, 95% CI: 0.05–0.8).

CONCLUSION: The HLA-DR locus seems to be associated with the genetic susceptibility to develop SNP in Mexicans.

EBM rating: B-2b

Analysis of genetic polymorphism of the HLA-B and HLA-DR loci in patients with dermatophytic onychomycosis and in their first-degree relatives

Onychomycosis is known to have predisposing factors and a high prevalence within families that cannot be explained by within-family transmission. We determined the frequency of HLA-B and HLA-DR haplotypes in 25 families of Mexican patients with onychomycosis in order to define the role of the class II major histocompatibility complex (MHC) in genetic susceptibility to this infection. Seventy-eight subjects participated in the study, 47 with onychomycosis and 31 healthy individuals. The frequencies of the HLA-B and HLA-DR haplotypes were compared with those found in first-degree relatives without onychomycosis and in a historic control group of healthy individuals. The frequencies in the controls were similar to those of the healthy relatives of the patients. However, on comparison of the patients with historic controls, we detected a higher frequency of the HLA-DR8 haplotype (P=.03; odds ratio, 1.89; 95% confidence interval, 0.98-36). These findings suggest that there are polymorphisms in genes of the MHC that increase susceptibility to onychomycosis, particularly haplotype HLA-DR8.

[Analysis of genetic polymorphism of the HLA-B and HLA-DR loci in patients with dermatophytic onychomycosis and in their first-degree relatives]

Onychomycosis is known to have predisposing factors and a high prevalence within families that cannot be explained by within-family transmission. We determined the frequency of HLA-B and HLA-DR haplotypes in 25 families of Mexican patients with onychomycosis in order to define the role of the class II major histocompatibility complex (MHC) in genetic susceptibility to this infection. Seventy-eight subjects participated in the study, 47 with onychomycosis and 31 healthy individuals. The frequencies of the HLA-B and HLA-DR haplotypes were compared with those found in first-degree relatives without onychomycosis and in a historic control group of healthy individuals. The frequencies in the controls were similar to those of the healthy relatives of the patients. However, on comparison of the patients with historic controls, we detected a higher frequency of the HLA-DR8 haplotype (P=.03; odds ratio, 1.89; 95% confidence interval, 0.98-36). These findings suggest that there are polymorphisms in genes of the MHC that increase susceptibility to onychomycosis, particularly haplotype HLA-DR8.

HLA class I and class II haplotypes in admixed families from several regions of Mexico

We studied HLA class I and class II alleles in 191 Mexican families (381 non-related individuals) to directly obtain the HLA-A/B/DRB1/DQB1 haplotypes and their linkage disequilibrium (LD). The most frequent HLA haplotypes observed were: A*02-B*39-DRB1*04-DQB1*0302, A*02-B*35-DRB1*04-DQB1*0302, A*68-B*39-DRB1*04-DQB1*0302, A*02-B*35-DRB1*08-DQB1*04, A*33-B*1402-DRB1*01-DQB1*05, and A*24-B*35-DRB1*04-DQB1*0302. The four most common haplotypes found by our study involve those previously reported in Amerindian populations. LD analysis of HLA-A-B and HLA-B-DRB1 loci showed significant associations between A29(19)-B44(12), A33(19)-B65(14), A1-B8, A26(19)-B44(12), A24(9)-B61(40), B65(14)-DR1, B8-DR17(3), B44(12)-DR7, B7-DR15(2), and B39(16)-DR4. Also, all DRB1-DQB1 associations showed significant LD values. Admixture estimations using a trihybrid model showed that Mexicans from the State of Sinaloa (Northern Mexico) have a greater proportion of European genetic component compared with Mexicans from the Central area of Mexico, who have a greater percentage of Amerindian genes. Our results are important for future comparative genetic studies of different Mexican ethnic groups with special relevance to disease association and transplantation studies.

Heritability of somatotype components: a multivariate analysis

OBJECTIVE

To study the genetic and environmental determination of variation in Heath-Carter somatotype (ST) components (endomorphy, mesomorphy and ectomorphy).

DESIGN

Multivariate path analysis on twin data.

SUBJECTS

Eight hundred and three members of 424 adult Flemish twin pairs (18-34 years of age).

RESULTS

The results indicate the significance of sex differences and the significance of the covariation between the three ST components. After age-regression, variation of the population in ST components and their covariation is explained by additive genetic sources of variance (A), shared (familial) environment (C) and unique environment (E). In men, additive genetic sources of variance explain 28.0% (CI 8.7-50.8%), 86.3% (71.6-90.2%) and 66.5% (37.4-85.1%) for endomorphy, mesomorphy and ectomorphy, respectively. For women, corresponding values are 32.3% (8.9-55.6%), 82.0% (67.7-87.7%) and 70.1% (48.9-81.8%). For all components in men and women, more than 70% of the total variation was explained by sources of variance shared between the three components, emphasising the importance of analysing the ST in a multivariate way.

CONCLUSIONS

The findings suggest that the high heritabilities for mesomorphy and ectomorphy reported in earlier twin studies in adolescence are maintained in adulthood. For endomorphy, which represents a relative measure of subcutaneous adipose tissue, however, the results suggest heritability may be considerably lower than most values reported in earlier studies on adolescent twins. The heritability is also lower than values reported for, for example, body mass index (BMI), which next to the weight of organs and adipose tissue also includes muscle and bone tissue. Considering the differences in heritability between musculoskeletal robustness (mesomorphy) and subcutaneous adipose tissue (endomorphy) it may be questioned whether studying the genetics of BMI will eventually lead to a better understanding of the genetics of fatness, obesity and overweight.

HLA genes in Mexican Teeneks: HLA genetic relationship with other worldwide populations

The HLA allele frequency distribution of the Mexican Teenek Indians has been studied and compared with those of other First American Natives and worldwide populations (a total of 15694 chromosomes from 73 different populations were analyzed). This study corroborate the restricted HLA polymorphism in the Amerindian populations and demonstrate how the Amerindians show a relatively homogeneity as opposed to other First Native American groups. Finally, the present data support previous ones that state the lack of complete correlation between language and genetics in micro-environmental studies; Teenek Mayan language does not correspond with a close Mayan (Guatemala) relatedness.

E-cadherin expression in sporadic gastric cancer from Mexico: exon 8 and 9 deletions are infrequent events associated with poor survival

Aberrant expression and mutation of E-cadherin is frequent in gastric carcinoma (GC) especially of the diffuse type. The frequency of CDH1 (gene encoding E-cadherin) mutation in populations with high incidence of diffuse GC and its prognostic significance is unknown. One hundred seventy-seven gastrectomies from Mexican mestizo patients with intestinal (53), mixed (55), or diffuse (69) GC were included. In addition, 101 endoscopic biopsies from patients with GC not subjected to surgery were analyzed. Immunohistochemistry against wild-type E-cadherin (clone 36) and against 2 mutation-specific antibodies (MSA) recognizing mutant CDH1 lacking exon-8 (del 8) or exon-9 (del 9) were performed. Staining was correlated with histotype, tumor node metastasis stage, and follow-up. Abnormal or absent E-cadherin expression (clone 36) was identified in 84% GC, predominantly in diffuse or mixed tumors (P = 0.004) in advanced stages (P = 0.003). No survival differences at 1 and 2 years were observed among patients showing normal, abnormal, or absent wild type E-cadherin expression. Overall reactivity with the MSA was observed in 10 (5.6%) patients who were treated with surgery. In 140 patients, dead from the disease or alive with the disease, the survival at 1 and 2 years was 37% versus 17% and 14% versus 0 for patients without and with del 8/9 positivity, respectively (log rank P = 0.01). Biopsies from patients with inoperable-GC (101) rendered 5 (4.95%) with del 8 or 9 immunoreactivity. Abnormal E-cadherin expression is frequent in GC. However, exon 8 or 9 deletions were observed in only 5.3% tumors in this series from Mexico, at a lower rate than previously published, but associated with a worse prognosis.

Comparative study of the residues 63 and 67 on the HLA-B molecule in patients with Takayasu's Arteritis

Takayasu's Arteritis (TA) has been associated with the Major Histocompatibility Complex (MHC) genes; nevertheless, results in several populations have been heterogeneous. Studies both in Mexican and Asian populations suggest that residues at positions 63 (glutamic acid) and 67 (serine) of the HLA-B molecule could be the genetic markers for TA. In the present work, we analyzed the sequence of HLA-B alleles in 26 TA patients and 62 healthy controls. HLA-B subtyping analysis showed that all B52 alleles were B*5201, whereas only one HLA-B39 allele was B*3902. Sequencing of HLA-B alleles showed that 19 out of 26 patients studied (73.0%) presented at least an allele with glutamic acid at position 63 and serine at position 67. This condition was observed in only 21.0% of the healthy controls (pC = 0.00001, OR = 10.23). Out of the seven remaining patients, one presented glutamic acid at position 63 and four showed serine at position 67. Two patients (2/26 = 7.7%) and 24 healthy controls (24/62 = 38.7%) did not show similarity at the mentioned positions (pC = 0.016, OR = 0.13). These data corroborate the participation of positions 63 and 67 in the genetic susceptibility to TA and explain the high heterogeneity of alleles associated with the disease in several populations.

Distribution of HLA-B alleles in Mexican Amerindian populations

In the present study we analyzed by PCR-SSO technique the HLA-B gene frequencies in 281 healthy individuals from four Mexican Amerindian populations (66 Mayos, 90 Mazatecans, 72 Nahuas and 53 Teenek). The most frequent alleles in all studied populations were HLA-B35, HLA-B39, and HLA-B40; however, some differences were observed between populations. The HLA-B35 allele was the most frequent in three of the four populations studied (Mayos, Nahuas and Teenek), whereas in Mazatecans the most frequent allele was HLA-B39. HLA-B40 presented frequencies higher than 10% in all groups. On the other hand, only Mayos presented an HLA-B51 gene frequency higher than 10%. When comparisons were made, important differences between groups were observed. The Teenek group presented an increased frequency of HLA-B35 when compared to Mazatecans and the HLA-B52 allele was increased in Nahuas and Teenek when compared to Mayos. An increased frequency of HLA-B39 was observed in Mazatecans when compared to Nahuas, Mayos and Teenek. Also, an increased frequency of HLA-B51 was observed in Mayos when compared to Mazatecans and Nahuas. These data corroborate the restricted polymorphism of HLA-B alleles and the high frequency of HLA-B35, HLA-B39 and HLA-B40 alleles in autochthonous American populations. In spite of the restriction in this polymorphism, differences in frequencies of HLA-B alleles could be helpful in distinguishing each of these populations.

Distribution of class I and class III MHC antigens in the Tarasco Amerindians

Class I and class III major histocompatibility complex (MHC) antigen frequencies were analyzed in 130 haplotypes from 33 families belonging to a group of Amerindians culturally and linguistically isolated for more than 12 centuries in Mexico: the Tarascos. The most frequent antigens in this ethnic group of the HLA-A locus are: A2 (gf 0.353), A24 (gf = 0.223), A31 (gf = 0.184), and A28 (gf = 0.161); and the most frequent of the HLA-B locus are: B35 (gf = 0.230), B39 (gf = 0.192), B15 (gf = 0.146), and B5 (gf = 0.123). On the other hand, class III antigens demonstrated relatively high frequencies of the SC31 (frequency = 0.561), SC01 (frequency = 0.076), and SC42 (frequency = 0.069) complotypes. Also important was the relatively high frequency of the HLA-B27 antigen (gf 0.061) and the SC33 complotype (frequency = 0.046), which are either absent or found infrequently in other Amerindian groups. Analysis of MHC haplotypes revealed that four of them have relatively high frequencies, these were the following: [B39;SC31] (11.6%), [B35;SC31] (11.6%), [B15;SC31] (8.0%), and [B5;SC31] (5.8%). Other MHC haplotypes had frequencies lower than 5.0%. The decreased frequency of BF alleles other than BF*S and the presence of the SC33 and SC32 complotypes suggest long time preservation from genetic admixture. This information withstands the basis for population genetic analysis and disease association studies in Mexican mestizos.

Class II allele and haplotype frequencies in Mexican systemic lupus erythematosus patients: the relevance of considering homologous chromosomes in determining susceptibility

The aim of the present study was to determine the relevant major histocompatibility complex (MHC) class II alleles in the genetic susceptibility to systemic lupus erythematosus (SLE) in Mexican Mestizo patients. We examined the gene and haplotype frequencies of the HLA-DRB1, DQA1 and DQB1 alleles by polymerase chain reaction-sequence-specific oligonucleotide probes in 81 Mexican SLE Mestizo patients and 99 ethnically matched controls. We found a significantly increased frequency of the HLA-DRB1*0301 (p(c) = 0.031, odds ratio = 2.63) allele and significantly decreased frequencies of the DRB1*0802 (p(c) = 0.035) and DRB1*1101 (p(c) = 0.037) alleles in the SLE group. Haplotype analysis showed increased frequencies of DRB1*0301-DQA1*0501-DQB1*0201 (p(c) = 0.017, odds ratio = 2.97), and decreased frequency of DRB1*0802-DQA1*0401-DQB1*0402 (p(c) = 0.034) in SLE patients. The most frequently detected haplotypes in SLE patients showed different haplotypic combinations in the homologous chromosome from those found in controls. Thus, the combinations detected in SLE patients were either not detected in the control group or infrequently found. The results suggest that the DRB1*0301 is the principal class II allele associated with the genetic susceptibility to SLE in Mexican patients and that the presence of a specific haplotype of the homologous chromosome in patients with DRB1*0407-DQA1*03-DQB1*0302 and DRB1*1501-DQA1*0102-DQB1*0602 haplotypes could have an additive effect on the susceptibility to the disease. Finally, the low frequency of the DRB1*0301 and DRB1*1501 alleles in the control population suggests that the genetic admixture between Mexican Indians and Caucasian populations was an event that could have increased the risk of Mexicans to develop SLE.

DNA sequencing of HLA-B alleles in Mexican patients with Takayasu arteritis

Takayasu arteritis (TA) is characterized by a 'pulseless' condition and occurs frequently in young females from Asian and South American countries. It has been associated with Mayor Histocompatibility Complex (MHC) genes in different populations. Recent data indicate direct participation of HLA-B alleles in the susceptibility to the disease. This fact was explored in an associative study with TA to establish if some region in the exon 2, intron 2 or in the exon 3 of HLA-B alleles is common in the alleles associated with TA and at the same time to know if a specific sequence or an epitope, more than an allele, would be responsible for the susceptibility to this vasculitis. We studied HLA-B alleles of 12 Mexican patients with TA using PCR-SSP and sequencing. The analysis by PCR-SSP in 12 patients showed that five of them showed the B*15 allele, three the B*40 allele and two the B*39 allele, the remaining two presented the B*44 allele. Sequence analysis enabled us to define that the B*39 subtypes are B*3908; B*15 subtypes are B*1510, B*1515, B*1522 and B*1531; and the B*40 subtypes are B*4005 and B*4008. An individual with B*51 (B*5107) and another with B*52 (B*5201) alleles were also identified. The sequences of the intron 2 seem be heterogeneous. Analysis at the 63 and 67 positions of HLA-B alleles showed that 9 of them have similarity in some of these positions with the residues detected in the B*5201 and B*3902 alleles associated with TA in Asian populations. The results indicate that there is heterogeneity in the alleles associated with TA in Mexicans but, in spite of that heterogeneity, the alleles associates can be separated into three groups: B*39, B*15 and B*40, whose subtypes are rare and apparently of recent generation in Mexico, probably by recombination events at intron 2 level. The sequences analysis also shows that most of the alleles detected in the Mexican patients share two epitopes described in the susceptibility alleles in Asian populations, suggesting that these epitopes could be responsible for the susceptibility to develop the disease in spite of the allele in which are found.

Genetic features of Mexican women predisposing to cancer of the uterine cervix

Cervical carcinoma is the most common neoplasia in Mexican women. Previous studies report association of this neoplasia with the major histocompatibility complex (MHC) antigens in Caucasians. In the present study, we compared antigen frequencies of class I and class II MHC phenotypes in patients and ethnically matched healthy controls. Patients had significantly increased frequencies of HLA-A2 (PC = .000003) and HLA-DR5 (PC = .01) as compared with healthy controls. Conversely, we found a significant decrease of HLA-DR6 (PC = .01), HLA-DR2 (PC = .0005) and HLA-DR1 (PC = .0009) as compared with healthy controls. These results confirm some previous studies on HLA-associations with cervical carcinoma and reinforce the theory of independent mechanisms of MHC class I and class II genes in the etiopathogenesis of this disease.

Hypopituitarism in Two Brothers Born by Breech Delivery

OBJECTIVE

To describe two brothers with hypopituitarism who had been born by breech delivery and to discuss whether this condition corresponds to a familial form or to a pituitary stalk section as a result of the breech delivery.

METHODS

We present the clinical, biochemical, and magnetic resonance imaging (MRI) characteristics of two Mexican brothers, 19 and 21 years old, with hypopituitarism and a history of breech delivery.

RESULTS

Physical examination of both patients showed short stature with normal body proportions, an obviously younger appearance than that expected for their chronologic age, high-pitched voice, irregularly positioned teeth, no axillary or pubic hair, and prepubertal genitalia. Biochemical testing showed low thyroxine and free thyroxine values with inadequate or normal thyrotropin, low basal testosterone, and mildly increased serum prolactin levels. Stimulation tests showed a normal and a delayed thyrotropin response to thyrotropin-releasing hormone, subnormal serum cortisol, considerably blunted growth hormone (GH) response to insulin-induced hypoglycemia, and absence of GH response to GH-releasing hormone in both cases. MRI showed an ectopic neuropituitary gland. In case 1, a caudal portion of a very thin pituitary stalk was observed, suggesting the preservation of a vascular component of the stalk. Because both parents of these brothers shared the major histocompatibility complex haplotype HLA-A*2301, B*3501, DRB1*0407, DQA1*03, DQB1*0201, consanguinity was suggested.

CONCLUSION

The phenotype of these patients differs from that described in families with POU1F1 (Pit-1) and PROP1 mutations. These cases are most likely related to an autosomal recessive gene mutation that warrants further research. To our knowledge, this is the first report of hypopituitarism in two brothers born by breech delivery.

Features of spondyloarthritis around the world

This article elucidates the prevalence and pathogenic roles of the MHC and microbial infections and clinical features and treatment of SpA across different populations from the arctic and subarctic regions to Central America, Asia, and Africa. Preliminary evidence suggests significant genetic and environmental influences on the onset and presentation of SpA, particularly AS, in these populations, which are different than those reported in white Caucasians; however, community surveys and longitudinal and case control studies are difficult to undertake in many of the developing countries. Thus, most of the currently available data have been devised from short-term and retrospective studies and should be treated with caution. Differences in referral and follow-up practices and the availability of rheumatology expertise and relevant resources may explain some of the differences observed in the populations discussed in this article. Furthermore, widely accepted criteria for the classification of SpA may not be applicable to non-Caucasians and need to be evaluated in these subjects. With gradual improvement in the economic status in many of the developing countries in Asia and Africa, it is hoped that with improvement in medical services, more physicians and specialty clinics in rheumatology, and changing referral patterns, better documentation of the various aspects of different SpA can be achieved. Future research should focus on the evaluation of specific risk or protective factors in population groups to better delineate the relative importance of genetic and environmental effects in the pathogenesis of SpA.

Intron 2 and exon 3 sequences may be involved in the susceptibility to develop Takayasu arteritis

We studied Major Histocompatibility Complex (MHC) Class I and Class II genes in seven Mexican Mestizo patients with Takayasu arteritis. Takayasu arteritis is an uncommon condition in Mexican Mestizo, however, previous studies report association of the disease in this population with Human Leukocyte Antigen (HLA)-B39 and HLA-DRB1*1301. The results in the present study show that the haplotypes of the Mexican Mestizo patients with Takayasu arteritis are very heterogeneous, even when the disease is much more rare in Mexico than in Japan. The sequence analysis of HLA-B39 shows that Mexican patients exhibit the HLA-B*39061 and HLA-B*39062 subtypes. These subtypes are more common in Mexico than in Japan, where the predominant subtype is HLA-B*3901. Interestingly, HLA-B*39061 and B-39062 share the 3' end of intron 2 and the 5' end of exon 3 with HLA-B*5101 and B*52012, alleles associated to Takayasu arteritis in Japanese. This fact suggests that Takayasu arteritis patients may share a specific sequence rather than a specific allele, even when the gene involved in the susceptibility to develop Takayasu arteritis may be a neighboring gene located between the genes related at present time with the disease, i.e. a gene located between MHC Class I and Class II regions.

Immunologic, genetic and social human risk factors associated to histoplasmosis: studies in the State of Guerrero, Mexico

Immunologic and occupational aspects of the susceptible population exposed to Histoplasma capsulatum, the causative agent of histoplasmosis were analyzed in the Mexican State of Guerrero. Three areas were studied, Juxtlahuaca, Olinala, and Coyuca; in the first two, their populations refer contact with bat guano and/or avian excreta, which contain nutrients for fungal growth, while the Coyuca population referred no contact with the above mentioned excreta. Previous infection with H. capsulatum was determined by histoplasmin-skin test, and the response was higher in men than in women (93.87, 85.71, and 6.6% for men, and 78.94, 66.6, and 0% for women) in Juxtlahuaca, Olinala, and Coyuca, respectively. Labor activities related to a persistent contact with the fungus were considered as an occupational risk factor, histoplasmin-skin test reached 88.57 and 36.36% of positive response in individuals with high and low risk activities. A high percentage of histoplasmin responses was observed in subjects with constant contact with H. capsulatum, such as, cave-tourist guides, peasants, and game-cock handlers, and generally they developed the largest diameter of skin reactions. Genetic risk factor was determined by studying the gene frequency of the Major Histocompatibility Complex antigens in a sample of individuals and their degree relatives in Juxtlahuaca, Olinala, and Coyuca. Significant differences were found for HLA-B22 and B17 antigens in Juxtlahuaca, and for HLA-B22 in Olinala, in comparison to the usual gene frequency observed in the normal Mexican population. HLA results were important, considering that HLA-B22 was previously found to be possibly related to pulmonary histoplasmosis in Guerrero.

HLA-DR6 (possibly DRB1*1301) is associated with susceptibility to Takayasu arteritis in Mexicans

Takayasu arteritis is characterized by a "pulseless" condition and occurs frequently in young females from Asian and South American countries. This disease has been found to be linked with major histocompatibility complex (MHC) antigens in Japanese individuals. In the present study we compared gene frequencies of class I, class II, and class III MHC genotypes in patients with Takayasu arteritis and ethnically matched healthy controls. Serological typing was confirmed by molecular typing at the DNA level. We found significant increases in the frequencies of human leucocyte antigen (HLA)-DR6 and HLA-B62 in patients compared to the healthy controls (P corrected [C] = 0.0007, relative risk [RR] = 5.08; PC = 0.05, RR = 3.13 respectively). However, since the number of patients was considerably lower than the number of controls this can be considered as a tendency and not a true association. On the other hand, we found a significantly decreased frequency of HLA-DR4 in patients compared to healthy controls (PC = 0.04, RR = 0.34). At the DNA level, all DR6-positive individuals were HLA-DRB1*1301 whereas controls were HLA-DRB1*1301 (4.2%). Takayasu arteritis in Mexicans is probably associated with the HLA-DR6 (DRB1*1301) gene.