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Biomedical subjects

K I Welsh

Publications and source records attributed to K I Welsh.

At least 163 records · Page 9Linked to original sources
PubMed1991

A family study confirms that the HLA-DP associations with celiac disease are the result of an extended HLA-DR3 haplotype.

Genotyping for HLA-DR, -DQ, and -DP antigens by restriction fragment length polymorphism (RFLP) analysis along with identification of restriction fragments associated with celiac disease (CD) were undertaken in 13 families in which more than one member had CD. Major histocompatibility complex class II haplotypes for the family members were constructed which included both genotypes and RFLP markers. In 12 of the families all the affected members shared an HLA haplotype which included HLA-DR3a, DQw2 and a BglII 4.0-kb DQA fragment. Eight of these 12 haplotypes also included HLA-DPw1 and both a RsaI 4.0-kb DPB fragment and an XbaI 16.0-kb DPA fragment. In one family, the two affected members shared an HLA-DR7, DQw2 haplotype, although both their second haplotypes included HLA-DR3a and -DQw2. The results suggest that HLA-DP genes do not play an independent predisposing role in the etiology of CD but do mark a disease-associated extended haplotype. This haplotype contains genes coding for specific HLA products which may be necessary for the disease to develop. The findings support the hypothesis that the presence of a specific DQ alpha/DQ beta heterodimer, encoded in a cis arrangement on HLA-DR3a haplotypes, predisposes to celiac disease.

Adolescent↗
PubMed1991

Immunoglobulin heavy chain gene polymorphisms in Italian patients with psoriasis and psoriatic arthritis.

A polymorphism of the switch region of the mu IgH gene (S mu) is associated with arthritis in English patients with psoriasis. In this study, Italian patients with psoriasis alone (PS) or psoriatic arthritis (PSA) were analysed by Southern blot using DNA probes for the S mu region and a hypervariable locus 5' of the joining (JH) region of IgH (5' JH). No association between PSA and IgH gene polymorphisms was found. However, an association was found between PS and a genotype of the 5' JH region (Fisher's P = 0.0002, RR = 27). Additional DNA markers around the S mu region may reveal more accurate markers for PS or PSA.

Arthritis, Psoriatic↗
PubMed1991

Genetic and environmental factors in scleroderma.

This review discusses possible markers of scleroderma, including fibronectin gene mutations, major histocompatibility complex class II antigens, anti-Scl-70, and the Fc receptor. The association between genetic and environmental factors is also reviewed, as is a mouse model of human disease.

Animals↗
PubMed1991

Application of polymerase chain reaction (PCR) to HLA-C locus typing.

Polymerase chain reaction/oligonucleotide typing was used to identify HLA-Cw*0601 (Cw6) in patients with psoriasis and psoriatic arthritis. The assignment of HLA-Cw*0601 was established by the concordant presence of codons for alanine (position 73), lysine (position 80) and tryptophan (position 97). The frequencies of all three codons were increased in the patient groups.

Arthritis, Psoriatic↗
PubMed1991

Influence of C4 null alleles on C4 activation in systemic lupus erythematosus.

Deficiencies of early components of the classical complement pathway are known to be associated with systemic lupus erythematosus (SLE). C4 null alleles, C4A Q0 and C4B Q0, are prime candidates for the major histocompatibility complex associated factor which determines susceptibility to SLE. There is poor correlation, however, between the presence of low concentrations of C4 and possession of C4 null alleles, and thus the basis of the association between C4A Q0, C4B Q0 and SLE remains obscure. The possibility that activation of C4 may be related to the possession of C4 null alleles was examined. C4 phenotypes were investigated, and C4 concentration and activation were estimated in patients with SLE. C4 activation was determined by measuring the concentration of C4d--a split product of C4. Twenty five of 35 patients had C4 phenotypes which include null alleles. No association between low C4 concentrations and C4 null alleles was found, but a significant association between low C4d concentrations and C4 phenotypes including null alleles, particularly those with C4A Q0, was noted. No correlation between concentrations of C4 and C4d was found. These results show an influence of C4 null alleles on the activation of the C4 molecule, which is independent of the concentration of C4. The possession of silent genes coding for C4 null alleles might predispose to SLE by conditioning poor C4 activation, a critical event for the clearance of immune complexes mediated by the classical complement pathway.

Alleles↗
PubMed1991

Major histocompatibility complex class II genes and systemic sclerosis.

1. In no ethnic group is the overall association between systemic sclerosis and the MHC strong enough for direct clinical use. MHC associations do support the classification of the disease into limited cutaneous systemic sclerosis and diffuse cutaneous systemic sclerosis. 2. Indications are that associations between specific subsets of patients with systemic sclerosis and genetic markers will assume greater importance both diagnostically and prognostically. The group with lung fibrosis look prime candidates, for example. 3. Genetic markers are useful means of relating chemically induced systemic sclerosis like disorders with the classical disease. Vinyl chloride disease provides an example. 4. Evidence is emerging of strong associations between certain genetic markers and autoantibody production; a similar story has emerged in systemic lupus erythematosus. We believe that, eventually, genetic tests will be used to influence treatment in at least a subset of patients with systemic sclerosis but that a dramatic breakthrough will not be made until we know how the genetics of the disease relate to the primary biochemical disease characteristic--that is, the overproduction of collagen. In this respect it has been suggested that the 5' flanking DNA of dermal collagen genes is particularly susceptible to the action of Scl-70 (topoisomerase I). A problem is how to tie this and the other observations discussed above together. The association of autoantibodies with topoisomerase I provides a tentative link between the MHC and collagen gene expression. Although the role and reason for anti-Scl-70 in systemic sclerosis is unknown, humoral autoimmunity, at least in systemic lupus erythematosus, seems to be strongly dependent on specific HLA genes. With an understanding of the function of MHC products at the molecular level, HLA and disease associations can now be analysed on a mechanistic level. For insulin dependent diabetes mellitus it has been shown that the MHC determined susceptibility to the disease is conferred by neutral residues (Val, Ser, Ala), at position 57 of the DQ beta chain, while Asp at this position correlates with resistance. A similar phenomenon has been described in rheumatoid arthritis. Although DR4 in general is associated with rheumatoid arthritis, it is heterogeneous, but a subtype of DR4 which is characterised by positively charged residues at positions 70 and 71 of the beta chains is not found in patients with rheumatoid arthritis (Wordsworth B P et al, unpublished data). A similar approach applied to the study of systemic sclerosis is likely to be similarly rewarding. The precise subtyping of the class II genes and the characterisation of their associated haplotypes is therefore required for a complete understanding of the contribution of the MHC to the disease. Additional genes linked to the MHC must not be overlooked, and are relevant to associations of haplotypes with the disease. Of particular interest are the recent reports of a new class of proteins, which are determined by genes in the MHC and which are considered to play a part in the assembly of the antigen peptide/MHC molecule complex.

Environmental Exposure↗
PubMed1991

HLA association with dermatitis herpetiformis is accounted for by a cis or transassociated DQ heterodimer.

HLA-DR, DQ, and DP restriction fragment genotyping was undertaken in 23 dermatitis herpetiformis patients and 53 healthy control subjects. HLA-DQw2 was present in 100% of patients with dermatitis herpetiformis (23 of 23) versus 40% of control subjects (21 of 53). Significant secondary associations occurred with HLA-DR3 (91% of patients versus 28% of control subjects) and DPw1 (39% of patients versus 11% of control subjects). Dermatitis herpetiformis and coeliac disease thus share an identical HLA class II association. It is likely that HLA class II genes directly influence the immune responses leading to mucosal damage in both diseases. The strongest candidate for disease susceptibility to dermatitis herpetiformis is DQw2. The HLA molecule most likely to be involved in coeliac disease is a specific DQ alpha/DQ beta heterodimer, encoded in cis arrangement in DR3 haplotypes or in trans arrangement in a DR5, 7 genotype. Our data on dermatitis herpetiformis patients fits this model perfectly. All these patients are capable of expressing this molecule, which may be responsible for the gluten sensitive enteropathy seen in a subgroup of patients with dermatitis herpetiformis and coeliac disease.

Celiac Disease↗
PubMed1990

Preliminary report: dramatic rise in renal allograft failure rate.

In 1989 the 1-year renal allograft survival at the Guy's Hospital paediatric transplant unit fell from 80% to 48%. The children were negative for HLA antibodies but 10 of the 21 were positive for an IgM antibody against epithelial cells (AEC). The 10 AEC-positive children had received a total of 12 grafts; 9 were lost and 3 were saved by means of plasma exchange. The 11 children without AEC received 11 grafts; 3 were lost, 2 owing to thrombosis. The correlation between the presence of AEC and graft rejection was highly significant. AEC have since been found in adult transplant recipients who suffered clinically similar graft failure, both at Guy's Hospital and at another hospital. The apparent spread of the antibody suggests an infective agent, but until the cause is identified kidney transplants in the paediatric unit have been suspended.

Adult↗
PubMed1990

Novel antibodies associated with unexplained loss of renal allografts.

Using an endothelial/epithelial hybrid cell line, three different non-HLA antibody types have been identified by flow cytometry in patients who have rapidly rejected multiple renal allografts. These antibodies may be classified as anti-endothelial-monocyte, anti-activated endothelial cell, or anti-epithelial cell.

Antibodies↗
PubMed1990

Celiac disease is associated with an extended HLA-DR3 haplotype which includes HLA-DPw1.

HLA-DP polymorphism was examined among celiac disease patients and controls. Restriction fragment length polymorphism (RFLP) genotyping showed a significant association of DPw1 in celiac disease (32/80) compared with controls (6/53, p = 0.0002). DPw1 typing by RFLP was verified using DPB1-amplified DNA and an oligonucleotide probe specific for the DPw1-associated DPB1 gene. The RFLP-assigned DPw1 genotype corresponded closely to the binding pattern of the sequence-specific oligonucleotide probe, although discrepancies did occur. The association between celiac disease and DPw1, however, remained. Oligonucleotide probe specificity was confirmed by sequencing DPB1-amplified DNA from four DPw1-genotyped celiacs. DPw1 is only present in celiacs who genotype DR3a-positive. Of DR3a controls 24% are DPw1-positive compared with 5% of non-DR3a controls (p = 0.03), suggesting that an extended DR3a, DPw1 haplotype occurs in the control population. This haplotype forms a large proportion of the DR3a haplotypes predisposing to celiac disease. Alternatively, DPw1 may represent an independent risk factor inherited in linkage with HLA-DR3 and -DQw2. Although predisposition to celiac disease is likely to be mediated by a specific DQ alpha/DQ beta heterodimer, a direct role for the DPw1 antigen cannot be discounted.

Base Sequence↗
PubMed1990

Sequence analysis of HLA-DR4B1 subtypes: additional first domain variability is detected by oligonucleotide hybridization and nucleotide sequencing.

The stimulating capacity of HLA-DR4 variants in mixed leukocyte culture correlates with variation in the polymorphic regions of the first domains of their DR beta 1 chains. Variability between amino acids 67 and 86 appears largely to determine HLA-DR4,Dw type. We have used a combination of a DR4B1-specific primer set in the polymerase chain reaction and specific oligonucleotide probes to examine DR4,Dw-associated nucleotide polymorphisms. Phenotype and gene frequencies are reported among 44 normal DR4 Caucasoids. Oligonucleotide probes were selected which enabled definition of Dw4-, w14-, w10-, w13-, and w15-associated sequences. Unexpectedly, several subjects were positive for Dw15 sequences which are usually characteristic of Oriental populations. Dw15 assignment was confirmed by nucleotide sequencing of DR4B1 polymerase chain reaction products. A pair of oligonucleotides informative for the glycine or valine dimorphism at position 86 was used to identify two novel DR4B1 alleles, designated 13.2 and 14.2. Nucleotide sequencing shows that these represent recombinants between third hypervariable regions associated with Dw13 and Dw14 and a codon for glycine at position 86 which is usually found associated with Dw4 and Dw15 sequences.

Alleles↗
PubMed1990

An HLA-associated nonresponsiveness to mellitin: a component of bee venom.

Previous work has demonstrated a close association between certain histocompatibility antigens and the gene that controls the IgE response to certain ragweed allergens. For example, there is a 90% association between IgE production to the short ragweed allergen, Amb a V, and an HLA class II allele. To assess whether these HLA linkages are specific for ragweed, we have investigated the association between HLA antigens and the capacity of individuals to mount a specific IgE response to melittin in patients with bee-venom allergy. Twenty-two subjects with bee-venom sensitivity, 22 healthy beekeepers without bee-venom allergy, and a normal population of 149 unselected individuals were studied. With serologic tissue typing and restriction fragment length polymorphism analysis, we have demonstrated a significant decrease in the HLA-DR4 and DQw3 alleles in subjects who are allergic to melittin compared to the control populations. There was also a negative association between the presence of HLA-DR4 and DQw3 alleles with the capacity of the individuals to mount an IgE response to phospholipase A2 (PLA2). The bee-venom sensitive subjects had a slightly lower titer of anti-PLA2 IgG when these subjects were compared to the bee-venom insensitive beekeepers. These results support the view that either HLA-DR or HLA-DQ has a protective role in controlling the IgE immune response. Lack of an IgE response to melittin or PLA2 is unlikely to be due to a failure to recognize allergen.

Adolescent↗
PubMed1990

Genes encoding the beta-chains of HLA-DR7 and HLA-DQw2 define major susceptibility determinants for idiopathic nephrotic syndrome.

1. We have investigated the frequencies of the major histocompatibility complex class II alleles by restriction fragment length polymorphism analysis, using DR, DQ and DP complementary DNA probes, in 40 Caucasoid steroid-sensitive nephrotic children. 2. A significant association with HLA-DR7 was demonstrated (P = 2 x 10(-5); aetiological fraction 0.6). The DQB1 gene of HLA-DQw2 was present in 83% of our patients (P = 2 x 10(-4); aetiological fraction 0.7). We present evidence that it contributes a second susceptibility allele. 3. A weak association between the uncommon HLA-DP-Cp63 allele and the disease was also observed. 4. Our data suggest that the immune events in steroid-sensitive nephrotic syndrome are defined by a particular immunogenetic background involving the beta-chain genes of HLA-DR7 and HLA-DQw2.

Adolescent↗
PubMed1990

Association of osteoarthritis with homozygosity for a 5.8 kb Taq I fragment of the alpha 1-antichymotrypsin gene.

The genes coding for the protease inhibitors alpha 1-antitrypsin (A1AT) and alpha 1-antichymotrypsin (A1ACT) were analysed by Southern blot in patients with rheumatoid arthritis, psoriatic arthritis, psoriasis without arthritis, polymyalgia rheumatica and generalized osteoarthritis. The probe/restriction enzyme combinations used were the 4.6 kb 5' fragment of the A1AT gene with the Sst I enzyme, the 6.5 kb 3' fragment of the same gene with Taq I and the 3.4 kb fragment of A1ACT with Taq I. The frequency of homozygous genotype for the 5.8 kb A1ACT band was increased in osteoarthritis (62.8% versus 36.8%, P = 0.01, relative risk = 2.9, aetiological fraction = 0.41). No other disease association was found with any marker. This suggests that the A1ACT gene may influence susceptibility to generalized osteoarthritis.

Alleles↗
PubMed1990

Immunogenetics of polymyalgia rheumatica.

Evidence suggests that polymyalgia rheumatica (PMR) may be an immune-mediated disease. Therefore, the role of HLA class II genes, the switch region of immunoglobin mu and alpha 1 heavy chain as the T-cell receptor (TcR) genes were investigated by Southern blot analysis. The frequency of DR4 specificity was increased in PMR (67.4% versus 30.3%; P = 0.00017). No association was found with the DQA and DQB genes, the switch region of immunoglobulin mu and alpha 1 heavy chain genes, and the TcR alpha, beta and gamma genes. This study suggests that HLA-DR4 is an important susceptibility factor for PMR. Further studies are needed to elucidate the role of Ig and TcR genes.

Alleles↗