HLA-antigens in oral submucous fibrosis.

HLA-typing was carried out on 122 areca nut chewers who attended hospitals for complaints unrelated to the habit. The subjects were South Africans of Indian extraction. The study did not include haplotypes. Palpable fibrous bands in the mouth indicated oral submucous fibrosis. The subjects were divided into 4 groups based on specific oral symptoms and signs. Groups A and B were without fibrous bands. Group A (47 subjects) included those with one or no symptoms while group B (28 subjects) suffered from 2 to 7 oral symptoms. Group C (17 subjects) had oral symptoms and represented early or mild oral submucous fibrosis and exhibited at least one discrete palpable fibrous band. Group D (30 subjects) were classic oral submucous fibrosis cases with multiple bands. The high occurrence of oral submucous fibrosis in this study group (39%) is similar to the occurrence in comparable age groups reported earlier in South Africa and is conceivably due to the higher age range of the subjects and their relatively long exposure to the areca nut. We were unable to demonstrate a specific pattern of HLA-antigen frequencies in chewers with or without the disease. Furthermore, there were no differences between the study population and the controls. It is concluded that there is not necessarily a HLA-associated susceptibility in oral submucous fibrosis.

Combinatorial diversity in DR2 haplotypes.

Sequence analysis has identified multiple alleles at two loci that encode for the DR2 specificity. The loci, DRB1 and DRB5, are in linkage disequilibrium which can extend to alleles of the DQ loci. Serologic, cellular, and sequence-specific oligonucleotide probe (SSOP) typing techniques have been used to identify the DR2 haplotypes. In this report, we have characterized by SSOP typing and cDNA/DNA sequence analyses the combinatorial diversity of DR2 haplotypes. Cells were selected on the basis of unique serologic reactivity, unique associations of alleles of DR and DQ loci, and/or presence in populations which have not been extensively characterized for HLA diversity. An asymmetric polymerase chain reaction (PCR) amplification was applied to rapidly screen unique cells and to characterize DNA sequence in conjunction with more conventional cDNA sequence analysis. The sequence data confirm the lack of a DRB5 locus in the DR2"LUM" specificity, the unexpected association of DRB1*1602 and DRB5*010 alleles in a nonCaucasoid population, and the association of the allele DRB1*1503 with DRB5*0101 in black African, African American and native American individuals. The DRB1*1503 and DRB5*0101 alleles were identified in an unusual haplotype, DR2,DQ2. The combinatorial diversity of the DR2 haplotypes is extended by these studies in nonCaucasoid populations.

Adult onset spinocerebellar ataxia linked to HLA in a South African kindred of mixed ancestry.

Hereditary spinocerebellar ataxia (SCA) is a relatively common disorder in the Western Cape region of South Africa. At present there are no genetic markers available for prenatal or presymptomatic diagnosis. A large kindred of mixed ancestry with late onset SCA was studied in which the disorder segregated in an autosomal dominant fashion. HLA typing was undertaken on 44 family members, and the HLA haplotypes were assigned on the basis of segregation. The LIPED computer program, with a correction factor allowing for the age of onset, was used to analyze the pedigree for linkage to HLA. Of 22 individuals in whom disease status could be definitely assessed, only one recombinant between HLA and the SCA locus occurred. The lod score reached a maximum of 4.13 at a recombination fraction of 0.05, indicating the odds to be approximately 13,500 to 1 in favor of linkage between HLA and the putative disease allele for SCA. A possible recombination within the HLA region suggested that the disease allele lies telomeric of the HLA region. In view of the recent demonstration of tight linkage between SCA1 and D6S89, however, HLA should not be used for presymptomatic diagnosis or genetic counselling.

Genetic linkage between Huntington disease and the D4S10 locus in South African families: further evidence against non-allelic heterogeneity.

A study of genetic linkage between Huntington disease (HD) and the D4S10 locus (G8) has been undertaken in 10 South African (SA) families originating from the black, white and mixed acestry population groups. Allele frequencies at the D4S10 locus have been established in the non-Caucasoid population groups. There are significant differences in the allele frequencies at the D4S10 locus between the various SA populations. Clearly, information about population-specific frequencies for all polymorphisms is essential prior to the implementation of predictive testing in different population groups. Linkage has been demonstrated within this mixed group of HD families in SA using the HindIII, EcoRI and MspI polymorphisms, detected by G8. A maximum lod score of 8.14 at a recombination fraction of 0.00 (confidence limit 0-0.058) has been calculated using a combined haplotype of the HindIII and MspI polymorphisms. Taking into account the diverse ethnic backgrounds of the different SA population groups in this investigation, the data obtained from the study provide further evidence that there is probably only a single HD locus.

HLA class II specificities and haplotypes in South Africa detected using polymerase chain reaction and sequence-specific oligonucleotide typing.

DNA sequencing of HLA class II alleles has revealed a degree of polymorphism much greater than was expected on the basis of the standard serological typing methods. Amplification of the polymorphic second exon of the class II genes using the polymerase chain reaction, followed by hybridization with sequence-specific oligonucleotide probes, allows the unambiguous identification of alleles which could not be detected previously. Using the protocols of the Eleventh International Histocompatibility Workshop, we have applied this procedure for the typing of several individuals and their families with suspected alleles that had been observed using serology, cellular typing and restriction fragment length polymorphism (RFLPs). These included an allele related to DRw8 and DRw14, which has only been observed in the mixed ancestral South African population. In addition, unusual combinations of class II genes forming unique haplotypic associations were seen.

Unusual HLA-DR,DQ haplotypes found in South African families of black, Asian Indian, and mixed ancestral origin.

Four non-Caucasoid families with the unusual HLA-DR,DQ haplotypes DRw17,DQw7; DR9,DQw2; DR4,DQw2; and DR4,DQw5 were studied. All four haplotypes showed identical serological patterns to those seen with the equivalent Caucasoid antigens, but no HLA-Dw specificities could be assigned. TaqI restriction fragment length polymorphism (RFLP) patterns observed using DRB, DQB, and DQA probes showed that the DRw17,DQw7 haplotype may have originated from a homologous crossover between a DRw17,DQw2 haplotype and a haplotype with DQw7. The results obtained for the DR9,DQw2 and DR4,DQw2 haplotypes suggest that these could have resulted from recombination events with an ancestral "black" DQw2 haplotype. From the RFLP data, it is difficult to postulate the origin of the DR4,DQw5 haplotype being from a single recombination event.

Spondyloepiphyseal dysplasia, mild autosomal dominant type is not due to primary defects of type II collagen.

A mild autosomal dominant form of spondyloepiphyseal dysplasia (SED) is present in several generations of a South African family of English stock. This phenotype differs from that of any other previously described. Although type II collagen defects have been found in some families with SED congenita, the phenotype in our family showed discordant segregation with COL2A1 gene associated restriction fragment length polymorphisms (RFLPs), the markers for the structural locus of type II collagen. It is evident that the SED group of disorders is heterogeneous.

The association between HLA and rheumatoid arthritis in Zimbabwean blacks.

HLA-A, B, C, DR and DQ typing was done on 26 black Zimbabweans with rheumatoid arthritis and the respective antigen frequencies were compared with those in a group of 119 normal individuals from the same ethnic background. Only the DR4 antigen was significantly increased in frequency in the patients, confirming the association with this disease seen in other Black African populations.

New HLA-DR2-related specificities detected in South African blacks and individuals of mixed ancestry.

This study describes a new HLA-DR2-related specificity DR2LUM (CT) present in South African Blacks and individuals of mixed ancestry (Cape Coloureds). It can be distinguished from the "classic" DR2 specificities. DRw15 and DRw16, using serological and Southern blot techniques. Although no HLA-Dw specificity could be assigned to the DR2LUM(CT) cells, borderline typing reactions with Dw2 HTCs were observed. Southern blot analysis using a DRB probe and the TaqI enzyme has shown that DR2LUM(CT) shared a 1.6 kb fragment with DRw15 and a 4.7 kb fragment with DR1 and DRw10, indicating sequence homology between DR2LUM(CT) and these alleles. In addition, another unusual HLA-DR2 haplotype was found. The DR antigen was typed serologically as DRw16 but showed a combination of restriction fragments which are associated with both the DRw15 and DRw16 specificities. This study demonstrates the value of investigating non-Caucasoid populations in further characterizing the polymorphisms of the HLA class II genes.

Polymorphism of DRw52 and its association with DRw11 and DRw12 in South African blacks (Negroes) and individuals of mixed ancestry (Cape coloreds).

The HLA-DRB3 gene, which encodes the supertypic HLA-DRw52 antigen, has been shown to have limited polymorphism. The alleles at this locus are also in linkage disequilibrium with the alleles at the DRB1 locus. We have studied 16 DRw11 and three DRw12 haplotypes in the South African populations. Five of the DRw11,DQw7 haplotypes were associated with a TaqI restriction fragment length polymorphism which has not been previously described and which correlated with the DRB3 gene. This new variant, which has been called DRw52d, is confined to individuals of black or mixed ancestry. Two of the DRw11,DQw7 haplotypes were also associated with DRw52a or DRw52c and not with DRw52b as has always been observed in white populations. The less common DRw11,DQw6 haplotype, observed in four individuals, also revealed different allelic associations with the DRB3 gene, together with an unusual DQA association. None of the three DRw12,DQw7 haplotypes had the usual association with the DRw52b allele and also demonstrated two distinct DQA associations. The pattern of linkage disequilibrium of the HLA-D region loci in the South African black populations is more complex than in other populations. These findings may be of significance for the matching of unrelated donors for organ transplantation, as well as the study of disease association with HLA.

Chemotherapy of adult acute nonlymphoblastic leukaemia.

Seventy-two consecutive and previously untreated adults with acute non-lymphoblastic leukaemia (ANLL), having a median age of 36 years (range 12 to 71), were prospectively randomised to receive conventional doses of cytosine arabinoside and doxorubicin combined with either etoposide (CTR III) or 6-thioguanine (DAT). Morbidity was comparable between the two regimens and complete remission (CR) rates of 52% and 62% respectively (p greater than 0.50) were not influenced by age above or below 50 years, initial white cell count, French-American-British classification, or race. However, growth pattern in the GM: CFUc assay was found to identify a subgroup of patients who had a significantly higher CR rate. Similarly, the secretion of tissue plasminogen activator by leukaemic blasts in vitro uniformly predicted for primary drug resistance, whereas a CR rate of 68% was associated with production of the urokinase type or a mixture of both enzymes. Remission duration and survival did not differ between these two forms of chemotherapy, nor were they influenced by immunotherapy with C. parvum or the duration of maintenance therapy, whereas age below 50 and the species of plasminogen activator secreted were significant prognostic factors. It is concluded that etoposide can be substituted for 6-thioguanine in these cytosine arabinoside and doxorubicin-containing regimens and that for both combinations the most sensitive prognostic factor for CR and survival is the species of plasminogen activator secreted in vitro by the leukaemic blasts.

Restriction fragment length polymorphism of HLA-DRw53 detected in South African blacks and individuals of mixed ancestry.

The HLA-DRw53 specificity has not until now been shown to demonstrate polymorphism. We have studied 33 DRw53 haplotypes, comprising 19 DR4, 10 DR7, and 4 DR9 haplotypes, from 6 homozygous typing cells, 11 families, and 8 random individuals. All the subjects studied were South African blacks or of mixed ancestry (Cape Coloureds), with the exception of four homozygous typing cells from whites. The DNA was digested with TaqI and, after Southern blotting, was hybridized with a full-length DRB cDNA probe. Fragments correlating with DR4 (5.5 kb), DR7 (4.0 kb), and DR9 (4.1 kb) were observed. Two fragments of 14.5 and 2.8 kb correlated with DRw53. In addition, two pairs of fragments demonstrated a diallelic pattern, which is likely to correlate with a polymorphism of the DRB4 (DRw53) gene, since one or other of the two patterns was observed in all cells carrying the DRw53 specificity. The first allelic pattern, called DRw53a, was characterized by the presence of 7.5- and 2.6-kb fragments, while the second pattern, called DRw53b, had 5.8- and 2.7-kb fragments. DRw53a occurred in 10 of the 19 DR4 haplotypes and 7 of the 10 DR7 haplotypes. All three DR9,DQw2 haplotypes were also associated with DRw53a. These findings may have important implications for disease associations and the use of unrelated donors for organ transplantation.

Association of rheumatoid arthritis with HLA in three South African populations--whites, blacks and a population of mixed ancestry.

The association between rheumatoid arthritis and HLA was studied in three South African populations: whites (N = 66), blacks (N = 33) and patients of mixed ancestry (Cape Coloureds) (N = 183). The antigens of the HLA-A, B, C, DR and DQ loci were detected by microlymphocytotoxicity assay and their frequencies in the three patient groups were compared with the corresponding frequencies in normal individuals of the same population group. HLA-DR4 was significantly associated with rheumatoid arthritis in whites (P less than 0.0001), blacks (P less than 0.001) and patients of mixed ancestry (P less than 10(-6]. The relative risk for HLA-DR4 was 3,2 in whites, 3,9 in blacks and 3,7 in patients of mixed ancestry. Other significant associations detected were with HLA-A2 in whites and HLA-B8 and DQw3 in patients of mixed ancestry. The constant association with HLA-DR4 seen in the different populations provides support for the suggestion that the HLA genes themselves are responsible for the genetic susceptibility to rheumatoid arthritis.

The polymorphism of HLA-DR3 in South African populations.

The polymorphism of HLA-DR3 was investigated in families and unrelated individuals of three population groups: South African (SA) Negroes, Cape Coloureds and SA Caucasoids. Serological and restriction fragment length polymorphism (RFLP) analysis indicated that DR3 could be subdivided into DRw17 (previously DR3.1) and DRw18 (previously DR3.2). In contrast, the two-dimensional (2-D) gel electrophoresis patterns could not distinguish between the DRB1 gene products of the HLA-DRw17 and DRw18 cells. Two DRB3 variants, correlating with the T-cell defined specificities Dw24 and Dw25 were identified at the genomic and product level. Of ten haplotypes studied with the newly defined HLA-DRw18 specificity, all had the DRB3 RFLP pattern associated with Dw24. HLA-DRw17 was found in all three population groups tested, although in the SA Negroes HLA-DRw18 was the prevalent DR3 subgroup. This subgroup was also present in the Cape Coloureds but was absent in the SA Caucasoids tested. HLA-DRw18 forms part of the most characteristic SA Negro haplotype, Bw42, DQw4, Dw"RSH," while HLA-DRw17 is part of the classic Caucasoid haplotype, B8, DQw2, Dw3.

Definition of the HLA-Aw43 antigen.

The HLA antigen Aw43 has been observed only in Southern African populations. In order to confirm its identity and clarify its definition, ten cells with this specificity were shipped to laboratories in England, the United States of America and Australia to be tested with the sera from the 10th International Histocompatibility Workshop. The results of tests on nine of these cells which were sufficiently viable indicated that HLA-Aw43 is a distinct serological specificity which could be distinguished from both the A10 cross-reacting group (A25, A26 and Aw34) and A29. The Aw43 specificity segregated in two South African Negro families, and occurred commonly in association with Bw70. The occurrence of HLA-Aw43 in South African Caucasoids, in contrast to its absence in other Caucasoid groups, is probably due to genetic admixture with indigenous South African populations.