Antonio Arnaiz-Villena

Implications of the polymorphism of HLA-G on its function, regulation, evolution and disease association

The HLA-G gene displays several peculiarities that are distinct from those of classical HLA class I genes. The unique structure of the HLA-G molecule permits a restricted peptide presentation and allows the modulation of the cells of the immune system. Although polymorphic sites may potentially influence all biological functions of HLA-G, those present at the promoter and 3′ untranslated regions have been particularly studied in experimental and pathological conditions. The relatively low polymorphism observed in the MHC-G coding region both in humans and apes may represent a strong selective pressure for invariance, whereas, in regulatory regions several lines of evidence support the role of balancing selection. Since HLA-G has immunomodulatory properties, the understanding of gene regulation and the role of polymorphic sites on gene function may permit an individualized approach for the future use of HLA-G for therapeutic purposes.

Primary Immunodeficiency Caused by Mutations in the Gene Encoding the CD3-γ Subunit of the T-Lymphocyte Receptor

PRIMARY immunodeficiency diseases are a heterogeneous group of disorders resulting from intrinsic defects of the immune system.1 They are frequently associated with repeated bacterial, fungal, or v...

The origin and spread of the HFE-C282Y haemochromatosis mutation

The mutation responsible for most cases of genetic haemochromatosis in Europe (HFE C282Y) appears to have been originated as a unique event on a chromosome carrying HLA-A3 and -B7. It is often described as a “Celtic mutation”—originating in a Celtic population in central Europe and spreading west and north by population movement. It has also been suggested that Viking migrations were largely responsible for the distribution of this mutation. Two, initial estimates of the age of the mutation are compatible with either of these suggestions. Here we examine the evidence about HFE C282Y frequencies, extended haplotypes involving HLA-A and -B alleles, the validity of calculations of mutation age, selective advantage and current views on the relative importance of “demic-diffusion” (population migration) and “adoption-diffusion” (cultural change) in the neolithic transition in Europe and since then. We conclude that the HFE C282Y mutation occurred in mainland Europe before 4,000 BC.

Relatedness among Basques, Portuguese, Spaniards, and Algerians studied by HLA allelic frequencies and haplotypes

Abstract HLA-A, -B, -DRB1, -DQA1, and DQB1 alleles were studied in Iberian and Algerian populations by serology and DNA sequence methodologies. The genetic and cultural relatedness among Basques, Spaniards, and paleo-North Africans (Berbers or Tamazights) was established. Portuguese people have also maintained a certain degree of cultural and ethnic-specific characteristics since ancient times. The results of the present HLA study in Portuguese populations show that they have features in common with Basques and Spaniards from Madrid: a high frequency of the HLA-haplotypes A29-B44-DR7 (ancient western Europeans), A2-B7-DR15 (ancient Europeans and paleo-North Africans), and A1-B8-DR3 (Europeans) are found as common characteristics. Portuguese and Basques do not show the Mediterranean A33-B14-DR1 haplotype, suggesting a lower admixture with Mediterraneans; Spaniards and Algerians do have this haplotype in a relatively high frequency, indicating a more extensive Mediterranean genetic influence. The paleo-North African haplotype A30-B18-DR3 present in Basques, Algerians, and Spaniards is not found in Portuguese either. The Portuguese have a characteristic unique among world populations: a high frequency of HLA-A25-B18-DR15 and A26-B38-DR13, which may reflect a still detectable founder effect coming from ancient Portuguese, i.e., oestrimnios and conios; Basques and Algerians also show specific haplotypes, A11-B27-DR1 and A2-B35-DR11, respectively, probably showing a relatively lower degree of admixture. A neighbor-joining dendrogram place Basques, Portuguese, Spaniards, and Algerians closer to each other and more separated from other populations. Genetic, cultural, geological, and linguistic evidence also supports the hypothesis that people coming from a fertile Saharan area emigrated towards the north (southern Europe, Mesopotamia, the Mediterranean Islands, and the North African coast) when the climate changed drastically to hotter and drier ca 10 000 years B.C.

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.

HLA allele and haplotype frequencies in Algerians

Abstract 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 calculae 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-Cw3-DR3-DQ2 and Al-B57-Ctv7-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.

Immunodeficiency associated with anorexia nervosa is secondary and improves after refeeding

Several studies have addressed the question of starvation effects on immune function by means of changes in lymphocyte subsets, cytokine induction or lymphocyte activation. Anorexia nervosa (AN) patients are severely malnourished and contradictory results have been obtained regarding the accompanying immunodeficiency, including its assignation as a part of the primary nervous disorder. In the present work, an extensive immunological function examination was carried out on 40 AN patients who were compared with a control group of 14 healthy girls. The AN patients were also classified according to their nutritional status (by the Body Mass Index: BMI), this being critical for a better understanding of these secondary immunodeficiency bases. Moreover, another immune system study was performed on five patients after refeeding. Lymphocyte subsets and function, cytokine induction and peripheral blood concentrations, and innate as well as humoral immunity were evaluated. Deregulation in the cytokine network, owing to the interaction of the central nervous (CNS) and immune systems, seems to be the initial immune alteration in AN immunodeficiency but it has not been disproved that the immunodeficiency is a direct consequence of the original psychiatric perturbation. Spontaneous high levels of circulating interleukin‐1β (IL‐1β) and tumour necrosis factor‐α (TNF‐α) have been observed; this is probably one of the causes of the anomalies found in the T‐cell subpopulations (mainly the naive CD4+CD45RA+ reduction and the cytotoxic CD8+ increase) and T‐cell activation status (mainly the down‐regulation of the CD2 and CD69 activation pathways). This finally leads to an impairment, not only in T‐cell function but also in T‐cell to B‐cell co‐operation. The AN specificity of these results is confirmed by the fact that these immune alterations improve after refeeding and when nutritional status becomes less critical, which also suggests that AN immunodeficiency is indeed secondary to malnutrition.

A new HLA-G allele (HLA-G * 0105N) and its distribution in the Spanish population

Six different HLA-G subtypes ( HLA-G*01011, -G*01012, -G*01013, -G*0102, -G*0103, and -G*0104) have been defined by the WHO Nomenclature Committee for Factors of the HLA System.HLA-G is an interesting nonclassical class I gene with the following characteristics: 1) a low degree of polymorphism (Morales et al. 1993; Yamashita et al. 1996); 2)HLA-G expression is restricted to trophoblast cells where it is the only Mhc molecule expressed; low mRNA transcript levels have been detected in a wide variety of cells in fetal and adult tissues (Onno et al. 1994); 3) alternative splicing of HLA-G transcripts gives rise to four membrane-bound and two soluble isoforms (Fujii et al. 1994); 4) polymorphic changes do not follow the three hypervariable regions per domain model and do not affect either the antigen or T-cell receptor binding sites (Arnaiz-Villena et al. 1996); and 5) stop codons have been found in homozygousity at theMhc-G exon 3 in the Cercopithecinaefamily of primates. Altogether this suggests that alternative splicing forms without exon 3 could play a role in cellular physiology other than antigen presenting (Castro et al. 1996). In the present study a new HLA-G subtype is described in the Spanish population; this allele shows linkage disequilibrium with the HLA A30-B13 haplotype and bears a nucleotide deletion either in the third position of codon 129 or the first of codon 130. Genomic DNA from 114 unrelated healthy Spanish individuals was isolated from peripheral blood lymphocytes using standard methods. Amplification of exon 2, exon 3, or exon 2 + intron 2 + exon 3 was performed using HLA-Gspecific primers as previously described (Morales et al. 1993). A total of 20 samples were further studied by singlestrand conformational polymorphism because they showed blanks or typing anomalies. Four showed a rare mobility pattern; polymerase chain reaction (PCR) products from exon 2 + intron 2 + exon 3 were purified, inserted into the pGEM-T vector, and sequenced in an Applied Biosystems (Foster City, CA) DNA automated sequencer. Two new HLA-G sequences were obtained: one ( HLA-G*0104, present in two unrelated samples) has been recently described in a Japanese population study (Yamashita et al. 1996), and the other (present in two other unrelated samples and namedHLA-G*0105N) has not yet been described. HLA-G*0104 has a non-synonymous leucine to isoleucine substitution at the first base of codon 110 (exon 3) compared withG*01013 (Fig. 1); this change is the first non-synonymous variation found at this codon in humans. This position does not seem to be important in the binding site region for processed antigen or in T-cell receptor interactions. A study of this allele in 114 unrelated Spanish individuals using a PCR-restriction fragment length polymorphism (RFLP) method (Morales et al. 1993) indicates that it is present in 100% of HLA-A23(n = 7)and 70% of HLA-A24 (n = 17)-positive Spaniards and has a frequency of 21.05% (n = 114, see Figure 1 legend). It is also found in four HLA-A19and oneHLA-A2/-A11-positive samples; strong linkage disequilibrium has already been described betweenHLA-A and -G alleles (Morales et al. 1993). The newHLA-G*0105Nallele shows a cytosine deletion either at the third base of codon 129 or the first base of codon 130 (exon 3; Fig. 1). This deletion changes the reading frame from this position, yielding a different amino acid sequence of the protein, which most likely would finish with a stop codon at the beginning of the α3 domain (exon 4), ifHLA-G*0105Nexon 4 DNA sequence is identical toHLA-G*01011 exon 4 DNA sequence; the cytosine deletion at codon 129/130 is not a PCR artefact because it has been observed in two different samples and in different PCR-RFLP assays. Stop codons in homozygousity have been found at exon 3 of Mhc-G sequences from The nucleotide sequence data reported in this paper have been subitted to the GenBank the nucleotide sequence database and have been assigned the accession number L78073. The name G*0105N was offficially assigned by the WHO Nomenclature Committee in October 1996

Familial defect in the surface expression of the T-cell receptor-CD3 complex.

INFANTS with severe combined immunodeficiency usually become ill in the first few months of life.1 Although growth and development proceed normally for a few months, length and weight gain cease, a...

Phylogeny and rapid Northern and Southern Hemisphere speciation of goldfinches during the Miocene and Pliocene Epochs

Abstract. Mitochondrial cytochrome b (cyt b) from 25 out of 31 extant goldfinches, siskins, greenfinches and redpolls (genus Carduelis) has been sequenced from living samples taken around the world, specimens have also been photographed. Phylogenetic analysis consistently gave the same groups of birds, and this grouping was generally related to geographical proximity. It has been supposed that Pleistocene glaciations played a crucial role in the origin of extant diversity and distribution of Northern Hemisphere vertebrates. Molecular comparison of most extant songbird species belonging to the genus Carduelis does not support this assertion. The fossil record of chicken and pheasant divergence time has been used to calibrate the molecular clock; cyt b DNA dendrograms suggest that speciation in Carduelinae birds occurred during the Miocene and Pliocene Epochs (9 – 2 million years ago) in both the Northern and Southern Hemispheres. Only about 4% average amount of nucleotide substitution per lineage is found between the most distant Carduelis species; this suggests a remarkably rapid radiation when compared with the radiation of other passerine songbird genera. In addition, a continuum of small songbird speciation may be found during the Miocene Epoch in parallel with speciation of other orders (i.e. Galliformes, chicken/pheasant). Pleistocene glaciations may have been important in subspeciation (i.e. Eastern European grey-headed goldfinches/Western European black-headed goldfinches) and also in ice-induced vicariance (isolation) (i.e. siskin in Western Europe vs. siskin in Far East Asia) around the world. European isolated Serinus citrinella (citril finch) is not a canary, but a true goldfinch. South American siskins have quickly radiated in the last 4 million years coinciding with the emergence of the Isthmus of Panama; probably, a North American siskin related to C. notata invaded a suitable and varied biotope (the South American island) for Carduelis birds. North American goldfinches may be renamed as siskins, because they have a distant genetic relationship with European goldfinches. Genus Acanthis could be dropped, and thus redpolls should be separated from twite and linnet, the latter (Europeans) probably being related to American goldfinches. Also, reproductive barriers are observed between closely related species and not between other more distant ones. Finally, a tentative classification for genus Carduelis species is suggested.