HLA antigens in a sample of the Spanish population: common features among Spaniards, Basques, and Sardinians

HLA associations with infliximab-induced liver injury

Biomarkers that are able to identify patients at risk of drug-induced liver injury (DILI) after treatment with infliximab could be important in increasing the safety of infliximab use. We performed a genetic analysis to identify possible human leukocyte antigen (HLA) associations with DILI in European Caucasian users of infliximab in a retrospective study of 16 infliximab-DILI patients and 60 matched controls. In infliximab-associated liver injury, multiple potentially causal individual HLA associations were observed, as well as possible haplotypes. The strongest associated HLA allele was HLA-B*39:01 (P = 0.001; odds ratio [OR] 43.6; 95% confidence interval [CI] 2.8-infinity), which always appeared with another associated allele C*12:03 (P = 0.032; OR 6.1; 95% CI 0.9-47.4). Other associations were observed with HLAs DQB1*02:01 (P = 0.007; OR 5.7; 95% CI 1.4-24.8), DRB1*03:01 (P = 0.012; OR 4.9; 95% CI 1.2-20.5), and B*08:01 (P = 0.048; OR 3.4; 95% CI 0.9-13.2), which also appeared together whenever present in cases. Additional associations were found with HLA-DPB1*10:01 (P = 0.042; OR 20.9; 95% CI 0.7-infinity) and HLA-DRB1*04:04 (P = 0.042; OR 20.9; 95% CI 0.7-infinity). A strong association with HLA-B*39:01 was identified as a potentially causal risk factor for infliximab-induced DILI. Future work should aim to validate this finding and explore possible mechanisms through which the biologic interacts with this particular allele.

Autosomal short tandem repeat genetic variation of the Basques in Spain

Aim

To examine population genetic structure and hypotheses of the origin of the modern Basque population in Spain using autosomal short tandem repeat (STR) data from individuals living in 27 mountain villages in the provinces of Alava, Vizcaya, Guipuzcoa, and Navarre, by comparing Basque autosomal STR variation with that of neighboring populations in Europe, as well as proposed ancestral populations in North Africa and the Caucasus.

Methods

Allele frequencies for 9 autosomal STR loci (D3S1358, D5S818, D7S820, D8S1179, D13S317, D18S51, D21S11, FGA, and vWA) and several population genetic parameters were determined for the 4 provinces in the Basque region of Spain (n = 377). Heterozygosity within the Basque population was measured using a locus-by-locus analysis of molecular variance. Relationships between the Basques and other populations were examined using a multidimensional scaling (MDS) plot of Shriver’s D_SW distance matrix.

Results

Heterozygosity levels in the Basque provinces were on the low end of the European distribution (0.805-0.812). The MDS plot of genetic distances revealed that the Basques differed from both the Caucasian and North African populations with respect to autosomal STR variation.

Conclusions

Autosomal STR analysis does not support the hypotheses of a recent common ancestor between the Basques and populations either from the Caucasus or North Africa.

Histocompatibility class I and II antigens in extensive kindred with Sneddon's syndrome and related hypercoagulation disorders

We have studied the relationship between the histocompatibility class I and II antigens and Sneddon's syndrome (SS) in a Spanish patient with SS and her relatives (13 available members of an extensive 3-generation pedigree with diverse autoimmune hypercoagulation abnormalities). The patient and her father were diagnosed with a primary antiphospholipid antibody syndrome and were HLA-A30-B13-Bw6. In addition, a HLA-Bw6-DQ1 association was present in all the members of this kindred. These data suggest that the combination of the histocompatibility class I and II antigens in this family may be a marker for predisposition to SS.

HLA alleles and haplotypes in French North African immigrants

Human leukocyte antigen (HLA) haplotypes (n = 187) were genotyped and assigned by the mode of inheritance in migrant families from North Africa who reside in the Paris, France, area. The distribution of alleles and haplotypes in that population was compared with the one obtained in a control population of ancient French natives residing in the same area (248 independent haplotypes also assigned by the mode of inheritance were studied). The results in migrants reveal the following: (1) a higher diversity in the distribution of HLA-A and -DRB1 alleles; (2) lower frequencies of alleles common in our region, such as A*0201 B*1501, B*4001, and DRB1*0401 and increased frequencies of minor subtypes, such as A*3002 and DRB1*0402; and (3) distinct distributions of B/Cw, DRB1/DQB1 or B/Cw/DRB1/DQB1 haplotypes. The results also revealed that the four most frequent five-allele haplotypes in controls i.e., HLA-A*0101/B*0801/Cw*0701/DRB1*0301/DQB1*0201; A*0301/B*0702/Cw*0702/DRB1*1501/DQB1*0602 (both of Indo-Celtic origin); A*2902/B*4403/Cw*1601/DRB1*0701/DQB1*0202 (frequent in Western-Europeans); and A*0201/B*1501/Cw*0304/DRB1*0401/DQB1*0302, represent 10.5% of the total haplotypes in controls but 1.6% in North Africans. Conversely, 9 five-allele haplotypes in multiple copy in North Africans (among which A*3002/B*1801/Cw*0501/DRB1*0301/DQB1*0201 of Paleo-North African origin and A*0201/B*0702/Cw*0702/DRB1*1501/DQB1*0602 of ancient European and Paleo-North African origin) represent 9.6% of the total haplotypes in North Africans but 2.4% in controls. These results thus suggest a low degree of admixture between the two populations.

BCG immunization at birth and atopic diseases in a homogeneous population of Spanish schoolchildren

BACKGROUND

The role of immunization with bacillus Calmette-Guérin (BCG) in the prevalence of asthma, hay fever and atopic dermatitis is not definitely established and seems to be influenced by ethnic background. The aim of this study was to analyze the relationship between this immunization and the prevalence of those diseases in a homogeneous population of Spanish schoolchildren.

METHODS

The International Study of Asthma and Allergies in Childhood (ISAAC) core and environmental questionnaires were used in four different centers of the Spanish North Atlantic coast. Bilbao, San Sebastián and Asturias have a universal BCG immunization policy during the first days of life, whereas La Coruña discontinued this practice in 1989. Except for this center, immunization coverage was above 90%. A random sample of schools of Asturias or all schools in the city district (rest of centers) with children 6 and 7 years old was surveyed.

RESULTS

The participation rate was above 70%. After excluding those children born outside Spain, the numbers were 6,762 immunized and 2,828 nonimmunized. After adjusting for gender, age, smoking habits of the father and mother, truck traffic near the household, older and younger siblings and having a cat or a dog during the first year of the child's life, the adjusted ORs of the BCG-immunized children suffering from asthma, hay fever and atopic dermatitis were respectively 0.87 (95% CI 0.76-1.00), 0.87 (0.75-1.01) and 0.89 (0.76-1.05).

CONCLUSIONS

BCG immunization offers a weak but significant protection against asthma and hay fever in Spanish schoolchildren.

High frequency of HLA-B44 allelic losses in human solid tumors

Human leukocyte antigen (HLA) class I downregulation, a frequent phenomenon observed in a variety of human tumors, favors tumor immune escape from T-lymphocyte recognition. However, it is not known whether a particular HLA class I allele is lost more frequently than others. To address this question we analyzed HLA class I expression in tumor tissues derived from 300 patients diagnosed as having breast, colorectal, or laryngeal carcinomas. Cryostatic tumor sections and a broad panel of anti-HLA class I monoclonal antibodies were used. We found that the HLA-B44 allele was lost more frequently than other HLA class I alleles, and that the difference was not related with changes in HLA-B44 allele frequencies between patients and controls. In addition, we observed that 35% of the HLA-B44 negative tumors presented HLA haplotype loss associated with loss of heterozygosity. These tests were performed on DNA samples obtained from microdissected tumor tissues. The results seem to indicate that HLA class I allelic losses are not randomly distributed during tumor development but that some HLA class I alleles, and HLA-B44 in particular, are more frequently downregulated and may play an important role in immune escape mechanisms.

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.

Frequency of the HFE gene mutations in five Italian populations

Genetic hemochromatosis is an autosomal recessive disorder characterized by iron overload and a variety of clinical manifestations such as liver cirrhosis and arthropathy. It is the most common genetic disease of northern European populations. The principal gene responsible for hereditary hemochromatosis, designated HFE, is located on chromosome 6 in the HLA region. The single point mutation 845A, changing cysteine at position 282 to tyrosine (C282Y), in this gene has been identified as the main genetic basis of hereditary hemochromatosis. Two other mutations, 187G, a histidine to aspartate at amino acid 63 (H63D), and 193T, a serine to cysteine at amino acid 65 (S65C), appear to be associated with milder forms of hereditary hemochromatosis. There is a high prevalence of the C282Y mutation in northern European populations, whereas in those of the Mediterranean basin the prevalence seems low and almost absent in Far East countries. This mutation seems usually to occur on the ancestral haplotype 7.1. Accordingly, a Celtic origin of this mutation has been suggested. The aim of this study was to determine the frequency of HFE gene mutations in five geographic regions in Italy. Samples were tested for C282Y, H63D, and S65C mutations of the HFE gene according to methods of each laboratory and the results were standardized with the exchange of typed samples between the different laboratories. In addition, C282Y-positive DNA samples were typed for D6S105 allele 8 and HLA-A3 by ARMS-PCR. We have found that the allele frequency of the C282Y mutation decreases from northeast Italy (Friuli, 6%) to northwest Italy (Piedmont, 4.8%) and to central Italy (Emilia-Romagna, 1.7%). However, this mutation is lacking in the two regions of the Mediterranean basin's center (Sicily and Sardinia). Accordingly, a significant difference in the frequency of the mutation was observed between these Italian regions (P = 0.07 x 10(-3)). In contrast, no difference was observed in allele frequency of H63D in the five Italian regions. Finally, as regards the S65C mutation a very low frequency was observed in Friuli, Emilia-Romagna, and Sardinia, whereas in Sicily and Piedmont we have not found this mutation. In conclusion, these data are consistent with the hypothesis that the C282Y mutation occurred in Caucasian populations of Celtic origin, whereas the H63D mutation is more ancient as demonstrated by the ubiquitous distribution.

HLA alleles and haplotypes in the Turkish population: relatedness to Kurds, Armenians and other Mediterraneans

Turkish and Kurdish HLA profiles are studied for the first time. The comparative study of their allele frequencies, characteristic haplotypes, genetic distances with other Mediterraneans is complemented by neighbor-joining dendrograms and correspondence analyses. Turks, Kurds, Armenians, Iranians, Jews, Lebanese and other (Eastern and Western) Mediterranean groups seem to share a common ancestry: the older "Mediterranean" substratum. No sign of the postulated Indo-European (Aryan) invasion (1200 B.C.) is detected by our genetic analysis. It is concluded that this invasion, if occurred, had a relatively few invaders in comparison to the already settled populations, i.e. Anatolian Hittite and Hurrian groups (older than 2000 B.C.). These may have given rise to present-day Kurdish, Armenian and Turkish populations.

The [HLA-B18, F1C30, DR3] conserved extended haplotype carries a susceptibility gene for IgD deficiency

We showed previously that the conserved extended MHC haplotype [HLA-B8, SCO1, DR3] carries recessive susceptibility genes for IgA and IgG4 deficiency and dominant genes for IgD and IgG3 deficiency. [HLA-B18, F1C30, DR3] has similar class II and III regions to [HLA-B8, SC01, DR3] and is common in the Basques. We therefore studied serum immunoglobulin concentrations in Basque homozygotes, heterozygotes, and noncarriers of (FIC30, DRB1*0301, DRB3*02, DQA1*0501. DQB1*0201) (F1C30, DR3). As shown by others, no subjects were deficient in IgA, IgM, or IgG subclasses. In contrast, 29% of homozygotes and three of seven double heterozygotes with (SC01, DRB1*0301, DRB3*0101, DQA1*0501, DQB1*0201) (presumed homozygotes for IgD deficiency susceptibility genes) were IgD deficient. Thus, 32% of presumed homozygotes were IgD deficient compared with 1.6% of noncarriers. Of haplotype heterozygotes, 25% were IgD deficient. The high frequency of IgD deficiency in both homozygotes and heterozygotes for (F1C30, DR3) suggests a partially penetrant dominant susceptibility gene for IgD deficiency on [HLA-B18, F1C30, DR3].

HLA genes in Arabic-speaking Moroccans: close relatedness to Berbers and Iberians

The gene profile of Arabic-speaking Moroccans has been compared with those of other Mediterranean populations in order to provide additional information about the history of their origins. Our HLA data suggest that most Moroccans are of a Berber (Imazighen) origin and that Arabs who invaded North Africa and Spain in the 7th century A.D. did not substantially contributed to the gene pool; however, they imposed their advanced culture and their religion. Present-day Egyptians are also related to Moroccan Berbers and this supports an ancient Saharan origin for part of the present-day Mediterraneans, particularly for the Arabic-speaking ones (also Algerians) and also for the older substratum of Mediterranean people.

The origin of Cretan populations as determined by characterization of HLA alleles

The Cretan HLA gene profile has been compared with those of other Mediterranean populations in order to provide additional information regarding the history of their origins. The allele frequencies, genetic distances between populations, relatedness dendrograms and correspondence analyses were calculated. Our results indicate that the Indoeuropean Greeks may be considered as a Mediterranean population of a more recent origin (after 2000 B.C.), while all other studied Mediterraneans (including Cretans) belong to an older substratum which was present in the area since pre-Neolithic times. A significant Turkish gene flow has not been detected in the Greek or Cretan populations, although Greeks and Turks have two high frequency HLA-DRB-DQB haplotypes in common. It is proposed that Imazighen (Caucasoid Berbers living at present in the North African coast and Saharan areas) are the remains of pre-Neolithic Saharan populations which could emigrate northwards between about 8000-6000 B.C., when desert desiccation began. They also could be part of the stock that gave rise to Sumerians, Cretans and Iberians; this is supported by both linguistic and HLA genetic data.

Linkage of house dust mite allergy with the HLA region

BACKGROUND

Atopy is a multifactorial disease, the pathogenesis of which is influenced by both genetic and environmental conditions. Genes in the HLA region have been involved in the control of the IgE response.

OBJECTIVE

In order to investigate whether allergy to house dust mite is associated with HLA in our population, we performed sib-pair analysis in 18 families and a case/control study of 161 non-related individuals.

METHODS

Levels of total and specific IgE were determined, skin-prick tests were carried out and clinical history was reviewed for every subject in the study. HLA class II typing was performed by the polymerase chain reaction with sequence specific primers.

RESULTS

We observed a significant difference from expected values in haplotypes shared by affected sibs; however, the case/control study did not reveal any association with any particular allele.

CONCLUSION

These results suggest that any particular HLA-DRB1/DQA1/DQB1 allele is responsible for the development of allergy to house dust mite in the Spanish population. Some other locus in or close to the HLA region might be involved, e.g., the tumour necrosis factor gene, a possibility that would explain the significant difference from expected values in the segregation of HLA haplotypes.

HLA DRB1-DQA1-DQB1 haplotype diversity in two African populations

HLA class II DRB1-DQA1-DQB1 haplotypic polymorphism was determined in 120 Liberian and 230 Gabonese individuals. In our study groups, the number of allelic variants observed for each locus was similar to that found in non-African populations. However, 39 novel haplotypes and several yet unrecognized DRB1-DQA1 and DQA1-DQB1 combinations were identified. The extent of HLA-haplotypic variability in Africans appears to result from the high degree of allele combinations rather than from allelic polymorphism.

Frequencies of HLA-A24 and HLA-DR4-DQ8 are increased and that of HLA-B blank is decreased in chronic toxic oil syndrome

The cause of toxic oil syndrome (TOS) has not yet been definitively determined, but some genetic susceptibility factors (certain HLA antigens and female sex) have been identified in 236 patients. Similarities with genetic factors for scleroderma and hydralazine-induced lupus (i.e. in TOS female sex and HLA-A24, Pcorrected = 0.00001 and DR4, Pcorrected = 0.04, respectively) may provide a clue to the responsible xenobiotic and its pathogenesis, and may also help in understanding the basis of the related eosinophilia-myalgia syndrome associated with tryptophan ingestion. In this paper it is also established that a human class I antigen (HLA-A24) and, independently, an HLA class II haplotype (DR4-DQ8, Pcorrected = 0.04) and arginine 52 in the alpha-DQ chains (Pcorrected = 0.03) are associated with TOS susceptibility, similarly to insulin-dependent diabetes. This further supports the classification of TOS as an autoimmune disease. Also, the increased frequency of a particular set of low-frequency HLA class I antigens in chronic TOS patients (i.e. B27, B37, B38 and B49) and the probable decrease in the frequency of HLA-B homozygotes in surviving patients (Pcorrected = 0.008) may provide an objective model to explain the maintenance of the HLA polymorphism: less frequent HLA alleles may be more advantageous in the event of unexpected human contact with unusual xenobiotics (not only microbes); however, other mechanisms working together to preserve and generate HLA polymorphism may coexist.

HLA DR and DQ polymorphism in Ashkenazi and non-Ashkenazi Jews: comparison with other Mediterraneans

HLA-DR and DQ alleles have been detected by DNA typing in Ashkenazi and non-Ashkenazi Jews from Israel. Allele frequencies, characteristic DR/DQ linkage disequilibria, population distances and their corresponding dendrogram by using the Neighbor-Joining method were used to study relatedness between Jewish and other Mediterranean and non Mediterranean populations. Closest relatedness is observed between Ashkenazi and non-Ashkenazi Jews, and, in decreasing order, also with Algerians, Spaniards (including Spanish-Basques), French and Italians. Also, particular characteristic Central European alleles are observed in Ashkenazi Jews and Mediterranean/African alleles in non-Ashkenazi Jews. This is consistent with historical data, Jews being an ancient Mediterranean population, who have had a certain degree of admixture with their 2000-3000 years old neighbors in spite of cultural and religious traditions which have preserved identity outside Israel.

HLA-B*1303: a new example of poor correlation between serology and structure

The HLA-B locus discloses a higher number of alleles and more complex serologic patterns than those observed for the HLA-A locus. In this article we describe the molecular structure and serologic details of a novel HLA-B allele, B*1303. B*1303 has been serologically defined as a B21 Bw4-associated molecule, whereas its primary structure is closely related to B13 alleles. In fact, only three nucleotide and two amino acid substitutions were found with respect to the Caucasian B*1302 allele. In contrast, there were 10, 14, and 16 amino acid substitutions when compared to B*4901, B*5001, and B*4005, respectively. Serologic analysis definitively supports the essential role of leucine 145 within the B13-specific epitope. Furthermore, the involvement of glutamic 163 in the definition of both the specific B21 and polyspecific B15,B57 epitopes is suggested. B*1303 constitutes a new example of how serology can give a distorted point of view of the structural relationship among alleles.

HLA allele and haplotype frequencies in Algerians. Relatedness to Spaniards and Basques

The powerful genetic polymorphism of the HLA system has been used to identify individuals and populations. Ethnic groups may be characterized by specific HLA allele frequencies and particular extended HLA haplotypes; also, genetic relationships among these groups may be deduced. In the present study, serology and DNA typing were used to detect HLA-A, -B, -C, -DR, and -DQ alleles in each individual and to calculate characteristic haplotypes in Algerians. These results were compared to those previously obtained in other populations, particularly northern Mediterraneans; genetic distances and their respective dendrograms place Basques and Spaniards closer to Algerians than to other Europeans. Also, characteristic Basque and/or Spanish haplotypes are found in Algerians; i.e., A30-B18-Cw5-DR3-DQ2 and A1-B57-Cw7-DR7-DQ2. This supports the evidence that the Algerian population, mainly its paleo-North African component (Berbers), has a common descent with Basques and Spaniards, probably reflecting a preneolithic relationship between Iberians and paleo-North Africans.

The contribution of the HLA-A, -B, -C and -DR, -DQ DNA typing to the study of the origins of Spaniards and Basques

The high polymorphism of the HLA system has been used as a powerful genetic tool to single out individuals and populations. By studying characteristic allele frequencies and extended HLA haplotypes in different populations, it is possible to identify ethnic groups and establish the genetic relationships among them. In the present study, HLA-A, -B, -C, -DR and -DQ typing at the serological/antigenic and the DNA level has been used for the first time to assign specific HLA frequencies and haplotypes to Spaniards and Basques and compare them with frequencies in other populations, particularly with North Africans. Allelic frequencies do not significantly differ between Spaniards and Basques. HLA genetic distances and their respective dendrogram together with the results on complete HLA haplotypes place Basques and Spaniards closer to paleo-North African populations than to other Europeans. This goes in favour of the Basques being a relative genetic isolate coming from the primitive Iberian/paleo-North African people. In addition, a tentative assignment of the most common Spanish HLA haplotypes to the different people who populated Iberia according to historical records has been done.

Molecular analysis of HLA-B27 haplotypes in Caucasoids. Frequencies of B27-Cw in Jewish and Spanish populations

PCR in combination with SSO probes was used to analyze the polymorphism in exons 2 and 3 of HLA-B27 subtypes and HLA-C-related alleles in two genetically distant Caucasian groups: Spanish and Jewish populations. AS patients and healthy B27 donors from both populations were analyzed in order to ascertain B27-Cw haplotypes. Three different ancestral haplotypes were found to be represented in both populations: B*2705/Cw*0102, B*2705/Cw*02022, and B*2702/Cw*02022. The B*2705 (92.5%) was the most frequent allele found in the Spanish population, carried by B*2705/Cw*0102 (60.9%) and B2705/Cw*02022 (30.4%) haplotypes. In contrast, B*2702 (59.4%) was the most prevalent allele found in the Jewish population and was carried by the B*2702/Cw*02022 (63.3%) haplotype. No different allelic and haplotypic distributions were among healthy and AS patients in either Spanish or Jewish populations. The differences found in the distribution of B27 haplotypes among Spanish and Jewish Caucasian populations are consistent with the genetic distance of these ethnic groups. When the Jewish population was subdivided into Ashkenazi (A) and non-Ashkenazi (NA) groups, no significant differences were observed in the distribution of B*2702/Cw*02022 haplotype. Minor differences were observed in the underrepresented B*2705 haplotypes. The present results reflect the ancestral affinities of A and NA Jewish populations. A possible HLA-B27 evolutive pathway in Caucasians is proposed according to the data available for the B27/Cw ancestral haplotypes in Spanish and Jewish groups.

Both class I and class II HLA antigens are thyroid cancer susceptibility factors

It has been established that HLA antigens are susceptibility factors for different cancers, including thyroid tumors. However, the diversity and sometimes weak and contradictory associations found have frequently led to the view that the HLA and tumorigenesis links might be the result of statistical errors. However, it has recently been established that it is indeed a currently complex and unexplained but real phenomenon, which may be crucial in preventing several types of cancer. In the present work we have found in a relatively large series of thyroid cancer patients (n = 161) that both HLA class I (B35) and class II (DR11) antigens are susceptibility factors only in the papillary tumor group of patients, B35 association p value is found at the limit of significance (pc(120) = 0.05); the follicular group did not show any HLA association, suggesting that the etiopathogenesis of each type of cancer is different. HLA-B35 and DR11 are not working together to induce tumorigenesis and each of them seems to confer susceptibility by using different pathways or by being markers of distinct neighboring susceptibility genes. DR4 has also been found in 86% (n = 6) of Hürthle cell carcinoma. No association has been found between HLA and disease activity. HLA mechanisms of association to cancer are discussed and a world-wide HLA/tumorigenic study is proposed to obtain a clear picture of the puzzling and controversial susceptibility markers found in different tumors and in different ethnic groups.

Identification of two different HLA B49 DR4 extended haplotypes in the Sardinian population

The HLA-B49 DR4 haplotype, which is rare in Caucasoid populations, has a frequency in Sardinia of approximately 6% and a very strong linkage disequilibrium (LD). To better understand its genetic structure, the Bf, C4A and C4B Class III alleles were studied in 56 healthy unrelated Sardinian subjects of B49 DR4 phenotype and in 24 of their families. Moreover, 14 sick subjects with the same phenotype were examined together with five of their families. A group of 285 haplotypes belonging to randomly selected individuals was used as a control population sampling. The distribution of the Bf, C4A and C4B alleles among the healthy probands revealed two main groups of association: one major group of 36 subjects (64.3%) with the BfF, C4A3 and C4B4 alleles and one minor group of 14 subjects (25%) with BfS, C4AQ0 and C4B1. A similar subdivision was also observed in the small group of patients. The family analysis confirmed these results and showed two different B49 DR4 extended haplotypes: one with the F34 complotype in 79.1% of the probands (delta x 1000 = 49.0) and the other with the S01 complotype in 20.8% of the probands (delta x 1000 = 17.3). The first one, in LD with the A1 and Cw7 alleles, has not yet been reported in other populations. The second one seems to be identical to a haplotype already reported in the Spanish population. The molecular analysis of the DRB1 locus carried out in 20 of the 70 probands demonstrated that, in both haplotypes, DR4 was represented by the DRB1*0405 allele.(ABSTRACT TRUNCATED AT 250 WORDS)

A decrease in the estimated frequency of the extended HLA haplotype B18 CF130 DR3 DQw2 is common to non-insulin-dependent diabetes, juvenile rheumatoid arthritis, and Berger's disease

Extended HLA haplotypes frequencies were estimated from the HLA, C2, Bf and C4 phenotypes of 74 patients with non-insulin-dependent diabetes (NIDD), 92 with juvenile rheumatoid arthritis (JRA), 44 with Berger's disease (BD), 83 with insulin-dependent diabetes (IDD), and 140 healthy controls. The extended HLA haplotype B18 CF130 DR3 DQw2, which is common (around 10% phenotype frequency) in healthy Spaniards and in other populations of paleo-North African origin, was found to be significantly less frequent in NIDD, JRA and BD, whereas its frequency was normal in IDD (although DR3 DQw2 haplotypes were increased in the latter disease). These data support the existence of a common HLA-linked pathogeneic mechanism in NIDD, JRA and BD, and point to a genetic difference between IDD and NIDD at the HLA level. This effect is readily detectable in our population because the uncommon BfF1 allele marks that haplotype instead of the more common BfS, which marks B8 CS01 DR3 DQw2 in other Caucasians. Our results support the hypothesis of strong selective pressures operating at the HLA level to preserve extended HLA haplotypes with advantageous gene sets from dilution by crossing-over. Imbalanced incomplete haplotypes may give rise to inappropriate T-cell repertoire selection in the thymus and/or antigen handling in the periphery, and be partly responsible for the pathogenesis of certain HLA-linked diseases (i.e. NIDD, JRA, and BD).

HLA frequencies in Basques in Spain and in neighbouring populations

HLA antigen and gene frequencies at the A, B, and C loci are examined in a sample of 181 Basques and 102 non-Basques in Bilbao, Spain. The most common associations of genes at the A and B loci are as in western Europe generally. The results are compared with gene frequencies in other Basque and non-Basque samples in Spain and France. There is clear distinction in gene frequency between Basques and non-Basques, to which the greatest contribution is made by A1 and B35, followed by B7, B8 and B12; and a difference between Basques in France and in Spain, notably in A28, 29, 30 and 31 and B17 and 18.

Evolutionary relationships of HLA-DR8 alleles and description of a new subtype (DRB1*0806) in the Algerian population

A new HLA-DR8 allele (HLA-DRB1*0806) found in the Algerian population is described here. This allele has an exon-2 nucleotide sequence identical to that of the HLA-DRB1*0801 allele, except for a GGT to GTG change in codon 86, yielding an amino acid substitution (glycine to valine). This change is also found in other HLA-DRB1 and HLA-DRB3 evolutionary-related allele pairs. HLA-DRB1*0806 is the most frequent HLA-DR8 allele found in this population (three of eight HLA-DR8-positive individuals) and is included within the HLA-DQA1*0102-DQB1*0602 haplotype (HLA-DQ6 serotype). This combination of HLA-DQ alleles is sporadically found associated with other HLA-DR8 alleles in other ethnic groups, i.e., HLA-DRB1*0804 in Bushmen and in North American blacks and HLA-DRB1*0803 in African blacks. Also, the HLA-DRB1*0806-DQ6 haplotype only bears one HLA-DRB gene copy, a common characteristic of the HLA-DR8 haplotype family. An exon-2 HLA-DR8 dendrogram has also been constructed with the available sequence data, indicating that this new allele does not seem to be placed at a distance significantly different from the origin to that of HLA-DRB1*0804 (proposed to be the eldest in the HLA-DR8 allele diversification pathway). A possible HLA-DR8 evolutive pathway is postulated according to the available exon-2 HLA-DR8 allele sequences.

HLA structure of the Sardinian population: a haplotype study of 551 families

A study on the HLA structure of the Sardinian population was carried out on 551 healthy unrelated families representing all of the island districts. Altogether 2202 HLA-A, B, Cw, DR individual haplotypes and 853 different haplotypes were determined. Cavalli-Sforza and Edwards' genetic distance index for the total of 62 tested alleles showed a modest heterogeneity between one district and another (0.09-0.16). The genetic distance between Sardinians and the rest of the Italian population was 0.23 (0.22-0.26) and progressively increased in comparisons with caucasoids (0.26), negroids (0.34) and mongoloids (0.41). Sixty-three two-locus haplotypes with a high positive linkage disequilibrium were observed in our family sample. The percentages of two-locus haplotypes in LD shared with other populations turned out to be 45% with caucasoids, 20% with negroids and 10% with mongoloids. The distribution of the A, B, Cw, DR haplotypes is shown with 673 of them represented only once or twice, and 10 (1.2%) 14-322 times each. Of the latter, 8 are extended haplotypes, 6 of which characterize the Sardinian population. The analysis of our data suggests that the present-day Sardinian population is the result of a superposition of different populations, mainly consisting of caucasoids on a pre-caucasoid paleo-Mediterranean substratum.

High frequency of the HLA-DRB1*0405-(Dw15)-DQw8 haplotype in Spaniards and its relationship to diabetes susceptibility

A study of DR4 subtypes has been done in Spanish unrelated controls and insulin-dependent diabetics by using dot blot hybridization with specific DR4B1 exon-2 oligonucleotides and automated dideoxy DNA sequencing. Dw15-DQw8 is the predominant DR4 subtype present in our normal population (37%); this DR4 frequency characteristic singles out our population from all other Caucasoids tested so far and may also be a marker of the original Iberian paleo-North African population. Dw15-DQw8 is not significantly increased in our insulin-dependent diabetics sample and despite its relative high frequency in the control population it does not have a bearing in lowering insulin-dependent diabetes mellitus frequency of DR4-positive Spaniards. In addition, no particular DR4 split is by itself significantly increased in Spanish diabetics; this may indicate that selective diabetogenic environmental factors may be working upon DR4-positive individuals, but on genes (or gene products) other than DR or at least not upon the polymorphic sites of DRB1 exon-2 products.

C4 Chido 3 and 6 distinguish two diabetogenic haplotypes: HLA-B49, SC01,DR4,DQw8 and B8,SC01,DR3,DQw2

The combination of the HLA complement allotypes BFS, C2C, C4AQ0 (deleted gene) and C4B1, termed SC01 complotype, usually present in the HLA-B8,DR3,DQw2 diabetogenic haplotype, has also been found in a novel "low frequency" HLA-B49,DR4,DQw8 haplotype associated with Spanish insulin-dependent diabetes mellitus (IDDM). Family studies of C4 antigenic determinants Rodgers/Chido and their specific C4d nucleotide sequences confirm that this novel haplotype bearing Chido -3, -6 is not due to a recent recombination from the common HLA-B8,DR3 haplotype bearing Chido 3,6; moreover, Chido analysis at the serological or DNA level is presently the only way to distinguish both SC01 complotypes, since BF, C2, steroid 21-hydroxylase and C4 genes do not reveal other differences by restriction fragment analysis. On the other hand, HLA-B49,SC01,DR4 is the first DR4-bearing IDDM-susceptible haplotype with a deleted C4 gene described so far and the only DR4-bearing haplotype found in the Spanish population. This report further supports the fact that extended haplotypes with deleted (or "not duplicated") genes in the class III region contain IDDM-susceptibility more often than non-deleted (or "duplicated") haplotypes in the Spanish and other Mediterranean populations.

T-lymphocyte dysfunctions occurring together with apical gut epithelial cell autoantibodies

Gut epithelial cell autoantibodies have been considered a hallmark of autoimmune enteropathy, a disorder occurring in children with protracted diarrhea of unknown etiology. Four patients (two male and two female) with such autoantibodies were studied. Immunofluorescence analysis showed two different disjunctive staining patterns: complement-fixing apical (three of four) and cytoplasmic (the remaining fourth one), which are shown to be directed against different structures. All three patients positive for complement-fixing apical gut epithelial cell autoantibodies had abnormal T-cell responses in vitro, one of them with an immunoglobulin G2 immunoglobulin deficiency and another with an immunoglobulin A deficiency. An immunoglobulin A deficiency without T-cell alterations was also diagnosed in the cytoplasmic gut epithelial cell autoantibody-positive patient. These findings suggest that different immunologic alterations (either a T-cell abnormality or immunoglobulin deficiency) may favor the appearance of gut epithelial cell autoantibodies (complement-fixing apical or cytoplasmic, respectively). Furthermore, these autoantibodies should not be considered a specific marker of autoimmune enteropathy, because they may not always be associated with such a disease: two patients with apical gut epithelial cell autoantibodies showed no signs of intestinal lesion or diarrhea.

DNA analysis of HLA-DR4B1 subtypes in multiple sclerosis by specific oligonucleotide probes

Conversely to the well-established association of DR2/Dw2 with multiple sclerosis (MS) susceptibility in Caucasoids, several studies have found an association of DR4 in populations from Mediterranean origin. We have studied the distribution of the different DR4B1 subtypes in Spanish MS patients. Oligonucleotide probes were selected in order to type samples amplified by polymerase chain reaction (PCR) from Spanish DR4+ MS patients (25) and controls (28). No DR4B1 subtypes were found to be increased in MS. MS susceptibility linked to DR4 may be due to the presence of shared functional epitopes common to the different HLA-DR4B1 subtypes.

Autoimmunogenic HLA-DRB1*0301 allele (DR3) may be distinguished at the DRB1 non-coding regions of HLA-B8,DR3,Dw24 and B18,DR3,Dw25 haplotypes

A novel TaqI restriction fragment length polymorphism (RFLP) of 4.15 kb is reported using a DR beta probe (pRTV1). This fragment corresponds to the DRB1 locus and allows the subdivision at the DNA level of the DRB1*0301 allele (DR3 antigen), which had not previously been reported. Both splits also distinguish each of the two DR3-bearing extended haplotypes (HLA-B8,SCO1,DR3,DQw2,Dw24 and B18,F1C30,DR3,DQw2,Dw25) found associated to several autoimmune diseases as insulin-dependent diabetes mellitus (IDDM), systemic lupus erythematosus (SLE) and myasthenia gravis. The fact that no polymorphism in the DRB1*0301 coding DNA sequence has been detected indicates that DRB1*0301 intronic, regulatory of neighbouring sequences might also contribute to differential disease associations (and pathogenic mechanisms) found linked to each of the two DR3-bearing haplotypes, i.e. IDDM and B8,DR3,Dw24 in North European/American Caucasoids vs IDDM and B18,DR3,Dw25 in Mediterraneans; SLE and B8,DR3,Dw24 in children vs SLE and B18,DR3,Dw25 in Spanish adults.

Low IgG2 and polysaccharide response in a T cell receptor expression defect

B lymphocytes require appropriate T lymphocyte cooperation to synthesize immunoglobulins (Ig). Such interaction presumably takes place after engagement of the T cell receptor (TcR) by antigen. The present work addresses B lymphocyte function (and phenotype) in a novel type of immunodeficiency which is characterized by a TcR expression defect. In contrast to expectations, the two affected siblings that were studied displayed normal in vivo antibody responses to both endogenous and exogenous protein antigens. However, they showed impaired responses to certain polysaccharide antigens together with a selective IgG2 deficiency. These results suggest that some polysaccharide responses may be more T cell dependent than previously suspected, and support the notion that T cell dysfunctions (of this or other kind), rather than Ig gene deletions, may be the molecular basis of certain IgG2 deficiencies. To rule out a concomitant gross B cell dysfunction in these individuals, B lymphocyte phenotype and function were assayed in vitro, and found to be normal. A T cell line derived from one of the siblings displayed an abnormal TcR on the cell surface, but it showed several normal TcR-mediated functions. This suggests that the low number of peripheral T lymphocytes that have been found to express low TcR levels in these immunodeficiencies may be operational, and supplying sufficient "help" for the observed normal antibody responses to all tested protein, but not polysaccharide, antigens.

Both HLA class II and class III DNA polymorphisms are linked to juvenile rheumatoid arthritis susceptibility

HLA-DR5 and DRw8 are not significantly linked to juvenile rheumatoid arthritis (JRA) in the Spanish population. However, we have found restriction fragment length polymorphisms (RFLPs) beta DR-2.9-kb-EcoRI and C4-14.3-kb-EcoRI, that correlate significantly with JRA. Eighty-six percent of our patients present either HLA-DR5 or the beta DR-2.9-kb-EcoRI allogenotope or lack the C4-14.3-kb-EcoRI allogenotope compared to 48% in controls; however, these particular DR and C4 RFLPs may not represent the corresponding DRB1 or C4 genes but rather neighboring ones which may be relevant to confer JRA susceptibility. The C4-14.3-kb-EcoRI RFLP decrease in patients may reflect a decrease in C4 B "long" phenotypes. Also, both RFLPs are the only markers able to identify most of the JRA patients in our population. On the other hand, the findings of both class II and III genes associated to JRA may reflect the existence of epistatic interactions (cis or trans) within the HLA gene cluster which lead to a particular pathology in certain diseases.

HLA antigens in multiple sclerosis of northern Spanish population

HLA-A, -B, -C, -DR, -DQ antigens were studied in 43 multiple sclerosis (MS) patients with clinically definite remittent sclerosis from Asturias (North Spain). The prevalence of HLA-B7, B7 and B27 were significantly increased in MS. HLA-B35 was under-represented in these patients. DR2 was increased but not significantly. No association with DQw1 was discovered. The existence of several susceptibility factors in the more common B7/DR2/DQw1 haplotype is discussed.

HLA antigens in psoriatic arthritis subtypes of a Spanish population

HLA-A, B, and C antigens were studied in 104 Spanish patients with psoriatic arthritis. Different clinical features were evaluated and the patients divided into disease subsets. HLA-B17, B27, B16, and Cw6 were the most common haplotypes in the total group. The HLA-B17/Cw6 haplotype was increased in patients with oligoarthritis. The increase of antigen B17 correlated with oligoarthritis and spondarthritis, whereas Cw6 was more significant in oligoarthritis. The prevalence of the B27/Cw1 haplotype was greater in association with spondarthritis and was probably related to the B27.5 subtype linked to Cw1. A significant negative association between the B44/Cw5 haplotype and psoriatic arthritis was found. The existence of several haplotypic factors in the different subsets is discussed. Lack of one or more HLA factors is thought to be responsible for the different clinical forms of psoriatic arthritis.

Shared SstI RFLPs by HLA-Aw19, A23/24 and A3/11 crossreacting groups

Three novel restriction fragment length polymorphisms (RFLPs) have been identified using a pan-HLA class I probe and the endonuclease SstI. This study, in conjunction with previously reported SstI RFLPs, now allows the identification of the HLA-crossreacting antigens Aw19 (A29/30/31/32/w33), A23/24 and A3/11 by specific hybridization patterns with a single enzyme/probe combination. Three of the corresponding polymorphic SstI restriction sites map within the HLA-A gene and generate two allelic RFLPs (5.06, 5.92 kb) and one single RFLP (5.92 kb) that show an absolute correlation with HLA-A23/24 and A29/32 crossreacting antigens, respectively. However, other SstI RFLPs (7.97, 9.4, 9.6, 9.8 and 13.34 kb), also linked to HLA-A crossreacting antigens, map outside the HLA-A gene and probably correspond to non-HLA-A,B,C class I genes in strong linkage disequilibrium with the HLA-A gene. These data show that HLA-A crossreacting antigens share more SstI RFLPs than neighboring non-HLA-A,B,C class I genes or pseudogenes; also, this has raised the possibility that some crossreacting HLA-A alloantisera might additionally recognize shared antigenic determinants in non-HLA-A,B,C proteins since the HLA-Aw19 crossreactivity cannot be fully explained by analyzing the HLA-A amino acid sequence.

Congenital heart block immunogenetics. Evidence of an additional role of HLA class III antigens and independence of Ro autoantibodies

Congenital complete heart block (CCHB) occurs in the offspring of mothers who have the HLA-A1;B8; DR3 haplotype and Ro (SS-A) autoantibodies. It has been shown that the presence of HLA-DR3 in mothers may facilitate Ro synthesis, but may not, by itself, be sufficient to induce CCHB in the offspring. However, maternal DR3 and Ro antibody seem to be independent factors associated with CCHB. Other HLA antigens, including class III (complement) genes, may also be necessary to induce CCHB in newborns since A1;B8; DR3 haplotypes, together with BfS and/or C4AQ0B1, are increased in Ro+ mothers of infants with CCHB compared with both controls and with Ro+ mothers whose offspring do not have CCHB. On the other hand, DR3 genes in a different HLA haplotype (i.e., B18; BfF1;DR3) are nonpathogenetic; this latter finding may be due to a DR3 gene's intrinsic difference or to the influence of neighboring genes. Also, a trend toward DR3 bias transmission is observed in DR3+ mothers who are also Ro+; fetal DR3 might protect the fetus against in utero death when Ro antibodies are present.

An Eco RI polymorphic site in the human complement C4 gene distinguishes juvenile rheumatoid arthritis (JRA) susceptibility-bearing haplotypes

Susceptibility to acquire Juvenile Rheumatoid Arthritis (JRA) is linked to HLA-DR5 and DRw8 antigens in Caucasoid populations. However, the frequency of HLA-DR5 is too high in the normal Spanish population and JRA cannot thus be found to be associated with this antigen. It has been found a 14.3 kb-C4-Eco RI restriction fragment length polymorphism which correlates significantly with JRA and may be used as a marker for this disorder in Spaniards.

Two BF F subtypes, but no BF S, BF F1 or BF S07 subdivision, are found by isoelectric focusing

When studied by immunoelectrophoresis the factor B (BF)*F allele is a monomorphic protein, but by using isoelectric focusing (IEF), it turns out to be polymorphic. Two BF*F allelic subdivisions, BF*FA and BF*FB, were detected in samples from unrelated Spanish donors; *FA and *FB are in Hardy-Weinberg equilibrium, segregate as autosomal codominant alleles in families, and BF*FA (but not BF*FB) is found to be in linkage disequilibrium with B44 and DR7 and is within the A29, B44, Bw4, Cx, CFA31, DR7, DRw53, DQ2 haplotype. Furthermore, BF FA individuals have a higher BF serum concentration than the BF FB individuals. The subdivision of BF S observed with IEF was found to be due to nonspecific BF S cleavage by serum proteases in inadequately collected or aged samples. Thus, the subdivision of BF S is spurious and was not found in our sera. BF F1 and BF S07 could not be further subdivided by IEF in our subjects. The BF F1 banding pattern was characterised by the presence of a cathodal band which corresponds to the Bb activation fragment. Finally, IEF combined with immunoblotting and monoclonal Ba and Bb antibodies may be used for accurately distinguishing BF phenotypes and doubtful bands.

Human MHC class III (Bf, C2, C4) genes and GLO: their association with other HLA antigens and extended haplotypes in the Spanish population

C4 allotype frequencies and their combination with factor B and C2 alleles (complotypes) were studied in a sample of the Spanish population in relation to MHC class I, class II and GLO alleles. The shorter genetic distances found for C4 between Spaniards and North Africans and the high frequency of extended HLA haplotypes (GLO 2) HLA-DR3 F1C30 HLA-B18 HLA-Cw5 (HLA-A30) and HLA-DR7 S1C21 HLA-Bw50 HLA-Cw6 are consistent with a paleo-North African ethnic origin (about 20,000 years B.C.) of a part of present Spaniards (Iberians), and with the effect of racial admixture during late Moslem invasions (from the 8th to the 15th century). The complotype null alleles C4A QO and C4B QO may be under natural selection pressure when found in cis position, since they are never in the same haplotype in families. The underestimation of these C4 null alleles' frequencies in unrelated individuals as compared to genotyped families is shown to be a very likely event and a serious hindrance for C4-disease association studies. We have not found any C4 duplications in the Spanish population; this may be due to sample size limitations or to the degree of admixture of our population. Strikingly, no positive linkage disequilibrium between C4A and C4B alleles is detected in unrelated individuals nor in families, although strong associations are maintained among Bf, C2, C4, HLA-A, HLA-B, HLA-C and HLA-DR markers. Assuming that all MHC polymorphisms have reached equilibrium, several explanations are proposed, including the possibility of no, different or additional natural selection mechanisms operating on some MHC class III genes (Bf, C2, C4 alleles combinations for most appropriate C3 convertases), as compared to those affecting class I and class II gene clusters (most advantageous immune response genes sets).

Immunofixation for C2 typing: C2 allotypes in Spaniards in relation to HLA, Bf and C4

C2 typing is performed by immunofixation with anti-C2 antiserum instead of by a hemolytic overlay. This method gives sharp band definition, is less cumbersome than the hemolytic overlay, gel files are easily made, and it also enables one to describe putative new nonhemolytic variants. C2 allele frequencies were studied in a sample of the normal Spanish population and were found to be similar to other Caucasoids. HLA-Bw62,-Cw3, and -DR4 were significantly associated with C2 B. Concordantly, the only C2*B extended HLA haplotype found in family material was Bw62-Cw3-Bw6-(DR4)-Bf*S-C2*B-C4A*3 B*2-(GLO*1). C4A*4 B*2 and C4A*4 B*4 are not found within the same haplotype together with C2*B and Bw62 or Bw22 respectively, nor do other C2*B haplotypes occur with common HLA-B alleles. These results may favour the hypothesis that the Bw62-C2*B haplotype is produced by one mutation arising in the Bw62-C2*C haplotype and that subsequent crossovers can explain other C2*B haplotypes (including Bw22-C2*B).

DR, C4, and Bf allotypes in juvenile rheumatoid arthritis

HLA-DR, C4, and Bf typing was performed in 99 patients with juvenile rheumatoid arthritis (JRA). DR1 was found with higher frequency in patients with polyarticular JRA than in controls (P less than 0.05). DR3 was more common in patients with fever and/or rash than in those without these manifestations (P less than 0.05). A significant negative association between JRA and C4A6 (P less than 0.05), C4BQ0 (P less than 0.0005), and BfF1 (P less than 0.05) was found. It is possible that a disequilibrium between DR and C4/Bf genes plays a role in the pathogenesis of JRA.

C3 polymorphism, HLA and chronic renal failure in Spaniards

C3 allele frequencies were studied in 196 unrelated normal Spaniards. The results fit the Hardy-Weinberg equilibrium. No rare variants were detected. The C3 frequency was close but slightly higher than that found in other Caucasoid populations, and higher than that found in Negroids and Orientals. Spanish Basques also showed a high C3F frequency. A North-South decreasing C3F gradient was recorded and compared to other gradients (HLA-D/DR, height, etc.) thought to be due to natural selection. Lod scores in 28 Spanish families excluded C3 gene assignment at less than 45 cM of HLA/GLO linkage group; no significant linkage disequilibrium was found between C3 and HLA. C3F was also significantly increased in 20 chronic renal failure (CRF) patients as compared to 196 controls; this would support the existence of functional differences between C3F and C3S alleles.

Severe hypertension in the Spanish population. Association with specific HLA antigens

There is now increasing evidence for immunological changes in essential hypertension. Immunological response is determined in part by genes linked to the HLA system. It has been reported a positive association between HLA B15 and the risk for cerebral events in essential hypertensive (EH) patients. We studied the distribution of HLA antigens in 128 EH (age range, 13-85 years) and 1000 normotensive controls. EH were classified in accordance with the World Health Organization (WHO) criteria: in WHO Stages I and II, there were 100 patients; in WHO Stage III, there were 28 patients. HLA-A and B antigens of peripheral blood lymphocytes were studied according to the microlymphocytotoxicity test. The results were compared by chi-square analysis, and the p value was multiplied by the number of antigens studied at each locus, to avoid overestimation of an association. Frequency of HLA-BW 22 was higher in EH compared with controls (5.4% vs 1.2%, p less than 0.01). Frequency of HLA-B12 in EH with WHO Stage III hypertension (64.2%) was significantly increased compared either with EH in WHO Stage I or II (29%, p less than 0.01) or the control group (26.9% p less than 0.001). The incidence of HLA-B15 antigen in the whole hypertensive group was 3.1%, lower than in normotensive controls (6.4%, p less than 0.8). None of the patients with WHO Stage III hypertension had the HLA-B15 antigen. In conclusion, the results seemed to indicated that the Spanish population had an association between HLA-B12 and severe hypertension.

Bf polymorphism and its relationship with HLA antigens in a sample of the Spanish Population: high BfF1 frequencies

Bf allele frequencies were studied in a sample of the normal Spanish population and in family haplotypes. BfF1 shows a frequency higher than in other Caucasoid populations and closer to that found in Negroids. Basques show an even higher BfF1 frequency BfF1 is in strong linkage disequilibrium with B18. HLA-Bw44 is found to be the B12 split in linkage disequilibrium with BfF and Bw50-BfS1 association is confirmed. DR3--BfF1 are not in linkage disequilibrium in the normal Spanish population, in contrast to DR3--BfF1 in linkage found in a diabetic Spanish population. Results are discussed on the bases of the paleo-North African Iberian population origins and of the use of Bf to define B12 and Bw21 splits.