Native American ancestry significantly contributes to neuromyelitis optica susceptibility in the admixed Mexican population.

Neuromyelitis Optica (NMO) is an autoimmune disease with a higher prevalence in non-European populations. Because the Mexican population resulted from the admixture between mainly Native American and European populations, we used genome-wide microarray, HLA high-resolution typing and AQP4 gene sequencing data to analyze genetic ancestry and to seek genetic variants conferring NMO susceptibility in admixed Mexican patients. A total of 164 Mexican NMO patients and 1,208 controls were included.

HLA Class I and II Blocks Are Associated to Susceptibility, Clinical Subtypes and Autoantibodies in Mexican Systemic Sclerosis (SSc) Patients.

Introduction: Human leukocyte antigen (HLA) polymorphism studies in Systemic Sclerosis (SSc) have yielded variable results. These studies need to consider the genetic admixture of the studied population. Here we used our previously reported definition of genetic admixture of Mexicans using HLA class I and II DNA blocks to map genetic susceptibility to develop SSc and its complications.

HLA class I and class II conserved extended haplotypes and their fragments or blocks in Mexicans: implications for the study of genetic diversity in admixed populations.

Major histocompatibility complex (MHC) genes are highly polymorphic and informative in disease association, transplantation, and population genetics studies with particular importance in the understanding of human population diversity and evolution. The aim of this study was to describe the HLA diversity in Mexican admixed individuals. We studied the polymorphism of MHC class I (HLA-A, -B, -C), and class II (HLA-DRB1, -DQB1) genes using high-resolution sequence based typing (SBT) method and we structured the blocks and conserved extended haplotypes (CEHs) in 234 non-related admixed Mexican individuals (468 haplotypes) by a maximum likelihood method.

Resolution of HLA class I sequence-based typing ambiguities by group-specific sequencing primers.

The increasing demand for allele-level human leukocyte antigen (HLA) typing has led the sequence-based typing (SBT) to become the preferred method. In turn, the steady increase in the number of HLA alleles driven by the adoption of SBT as the ultimate typing method leads to the ever increasing number of cis/trans ambiguities. Over the last few years, additional sequencing with the commercially available group-specific sequencing primers (GSSPs) has replaced sequence-specific primer-polymerase chain reaction and group-specific amplification as the means of resolving cis/trans ambiguities in many laboratories.

New HLA-C alleles identified in minority populations.

Twenty new human leukocyte antigen C alleles identified in 2200 minority individuals characterized by sequence-based typing.

The recombinant HLA-B*5518 allele supports the evidence of conserved haplotype association of rare alleles.

Allelic polymorphism of the major histocompatibility complex arises mostly from gene recombination. Intralocus gene recombination usually involves short fragments of DNA leading most commonly to single-nucleotide substitutions and rarely involves large fragments. Here, we report a new recombinant human leukocyte antigen (HLA)-B*5518 allele that has arisen via recombination of a large fragment of DNA spanning more than 70 nucleotides.

HLA-Cw*1214 allele arisen via recombination between HLA-Cw*070201 and HLA-Cw*120201.

Allelic polymorphism of the major histocompatibility complex arises mostly from gene conversion. Intralocus gene conversion usually involves limited fragments of DNA, whereas recombination involving large fragments of DNA is considered to be a rare event. During routine sequencing-based typing of donors for the National Marrow Donor Program, a new HLA-C allele was identified in a Caucasian donor.

Typing of HLA-B*15 alleles using sequence-specific primers.

We have developed a DNA based typing method to detect 38 known B*15 alleles using sequence-specific primers (PCR-SSP). This method involves 38 primers and 39 PCR-SSP reactions with results that can be obtained in 3 hours. The method is easy, fast and suitable for clinical typing for bone marrow and organ transplantation.

Error rate for HLA-B antigen assignment by serology: implications for proficiency testing and utilization of DNA-based typing methods.

Until recently, the majority of HLA class I typing has been performed by serology. Expensive commercial typing trays are frequently used for testing non-Caucasian subjects and new strategies using DNA-based methods have been adopted for improving clinical histocompatibility testing results and adapted as supplements in proficiency testing. A double-blind comparison of the typing of HLA-B specificities in 40 samples was carried out between serology and two polymerase chain reaction (PCR) methods, PCR amplification with sequence-specific primers (PCR-SSP) and PCR amplification and subsequent hybridization with sequence-specific oligonucleotide probes (PCR-SSOP).

Accurate typing of HLA-A antigens and analysis of serological deficiencies.

We are reporting the results of HLA-A typing by PCR-SSOP complemented by PCR-SSP of samples obtained from the National Marrow Donor Program (NMDP). These samples were a representative group from 2486 tested in duplicate by serology. A total of 390 samples gave HLA-A discrepant results.

Analysis of HLA-A and -B serologic typing of bone marrow registry donors using polymerase chain reaction with sequence-specific oligonucleotide probes and DNA sequencing.

Unrelated volunteer donors (69) recruited by the National Marrow Donor Program were HLA typed by DNA-based methods for both the HLA-A and -B loci. Each donor had been previously typed by serology by at least two independent laboratories. Of the 69 samples, all serologic laboratories were in concordance for HLA-A in 62 typed samples and for HLA-B in 48 typed samples.

New HLA-DR haplotypes containing the DRB6 pseudogene.

An unexpected probe reaction pattern was observed in two samples during HLA-DR typing by PCR-Sequence Specific Oligonucleotide Probes. In order to confirm the unusual typings, samples were analyzed by PCR-Sequence Specific Primers, cloning, and nucleotide sequencing of the second exon of the HLA-DRB-genes. The confirmed DR, DQ phenotype for one sample was DRB1*0701, DRB4*01, DRB5*0101, DRB6*0201, DQB*0602, DQB1*0202.

Comparison of HLA-A antigen typing by serology with two polymerase chain reaction based DNA typing methods: implications for proficiency testing.

Serology has been routinely used for class I HLA typing for the selection of donors for allotransplantation. However, serology is not adequate for the assignment of all class I specificities especially when testing non-Caucasians subjects and it is necessary to adopt new strategies for routine testing. At the present time the extent of incorrect serologic HLA-A assignments in clinical testing is not known.

Unrelated donor matching for bone marrow transplantation.

We found that in our laboratory the MLC was interpretable in most cases, in spite of patient disease state and shipping blood from unrelated donors over great distances. Our data clearly show that DRB1 allele typing was a good predictor of MLC reactivity and we believe that MLC testing in DRB1 allele mismatched unrelated pairs is not informative. However, our data suggest that MLC testing in DRB1 allele matched unrelated pairs is informative, because many such pairs produced weak but significant allostimulation.

HLA-DPB1 allele mismatches between unrelated HLA-A,B,C,DR (generic) DQA1-identical unrelated individuals with unreactive MLC.

We have used a PCR-RFLP method with one generic amplification of HLA-DPB1 second exon and 6 endonucleases to differentiate the 19 HLA-DPB1 alleles and 171 heterozygous combinations. The set of primers used in our studies produced fragment sizes different from those published before (1). The HLA-DPB1 alleles in Caucasians showed a higher frequency of DPB1*0401 and DPB1*0402, when compared to a small group of Colombians who showed a higher frequency of DPB1*0402 and DPB1*0201.

HLA-DQA1 and MLC among HLA (generic)-identical unrelated individuals.

We modified a previously published PCR-RFLP for DQA1 typing (1) and examined the predictive value of HLA-DQA1 in mixed lymphocyte cultures (MLC) among matched (HLA generic types) pairs of unrelated individuals. There were 61/102 (60%) pairs with positive MLC, one-third of which could be predicted by DQA1* typing alone. DQA1 matching and MLC reactions were classified into 3 groups: 1) DQA1 mismatches showing positive MLC: 19/102 (19%); 2) DQA1 matches showing negative MLC: 41/102 (40%); 3) DQA1 identical showing positive MLC: 42/102 (41%).

Complotypes in individuals of African origin: frequencies and possible extended MHC haplotypes.

We analyzed the frequency distribution of 106 complotypes [four allele sets of the major histocompatibility complex (MHC) genes for the complement proteins factor B, C2, C4A, and C4B] from 32 Black families residing in Boston and Washington, DC. Twenty-five different complotypes were identified, among which there were four complotypes that had not been previously observed in our large database of complotypes compiled from family studies of Boston Caucasians and that are, presumably, unique to individuals of African origin. These four African-derived complotypes are FC(1,90)0, FC63, S1C2, 17, and SC(3,2,90)0.

HLA-DQ RFLP variants of five HLA-DQw2-bearing major histocompatibility complex extended haplotypes.

We have analyzed genomic DNA in a large number of independent examples of five HLA-DQw2-bearing extended haplotypes for their associated subtypes by restriction fragment length polymorphism (RFLP) using DRB, DQA, and DQB probes after Taq I and Pst I digestion and Southern blotting. In addition to three previously described HLA-DQw2 subtypes, DQw2a, DQw2b, and DQw2c, we observed a fourth subtype, HLA-DQw2d, characterized by 5.8 kilobase (kb) DRB/Taq I, 2.

Characterization of HLA-Bw73 by serology and one-dimensional isoelectric focusing patterns.

The HLA-Bw73 antigen has been characterized by antisera in the Ninth International Histocompatibility Workshop. The International Workshop antibodies 9w245, 9w246, and 9w247 detected HLA-B7 and one or more antigens of this group (HLA-B40, Bw22, Bw42, or Bw48) in addition to HLA-Bw73. We have serologically characterized three additional antibodies, in two family studies, which contain anti-Bw73 (two of the antisera also contain anti-B7 activity).

Unrelated individuals matched for MHC extended haplotypes and HLA-identical siblings show comparable responses in mixed lymphocyte culture.

Extended haplotypes are specific HLA B, HLA DR, BF, C2, C4A, and C4B combinations in significant linkage disequilibrium in chromosomes of unrelated individuals. The possibility that matching unrelated individuals for extended haplotypes may match for the genes that cause mixed lymphocyte reactivity was tested. 22 of 26 unrelated extended-haplotype-matched subjects had similar mixed lymphocyte reactivity to HLA-identical siblings.

HLA antigens of insulin-dependent diabetics. I. PLT colonies detecting Dw10 and a new class II determinant distinct from HLA-D, DR, MB(DC), MT, and SB.

We describe three human proliferating T cell colonies, derived from mixed leukocyte culture with a non-diabetic individual (DR3 + 4) as the source of responding cells and an insulin-dependent diabetic patient (also DR3 + 4) as the source of stimulating cells. One colony detects HLA-Dw10 or a closely related antigen, and two detect an antigen that we call BO1 (Boston 1). BO1 is found so far on cells of all persons with DR5, about half of those with DRw6, and a particular subset of those with DR3.

Linkage disequilibrium of HLA-SB1 with the HLA-A1, B8, DR3, SCO1 and of HLA-SB4 with the HLA-A26, Bw38, Dw10, DR4, SC21 extended haplotypes.

Homozygous typing cells from 13 normal HLA-A1, B8, Dw3, DR3 and five normal HLA-A26, Bw38, Dw10, DR4 individuals were typed for the following markers: HLA-SB, MB, MT; complement proteins BF, C2, C4A, C4B; and GLO. Ninety-one percent of A1, B8, Dw3, DR3 homozygous individuals (HI) tested were homozygous for BF*S, C2*C, C4A*QO, and C4B*1 (SCO1 complotype), which indicates that the SCO1 complotype is in linkage disequilibrium with the A1, B8, DR3 haplotype in randomly selected normal populations. Sixty-seven percent of HLA-A1, B8, Dw3, DR3, SCO1 positive HI also expressed SB1; since the frequency of SB1 in random Caucasian populations is 11.

Extended MHC haplotypes in 21-hydroxylase-deficiency congenital adrenal hyperplasia: shared genotypes in unrelated patients.

HLA, complement, and glyoxalase I alleles were studied in 29 families in which at least one member has classical 21-hydroxylase-deficiency congenital adrenal hyperplasia. A rare complement allele, C4B*31, was found in over 20% of the haplotypes defined in these families and was always part of the complement haplotype BF*F, C2*C, C4A*Q0, C4B*31 (abbreviated FCO,31). The haplotype containing this rare set of complement alleles always carried the rare HLA allele, HLA-Bw47, usually carried HLA-A3, and almost always had the alleles HLA-Cw6, HLA-DR7, and the glyoxalase I (GLO) allele GLO1.