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E D du Toit

Publications and source records attributed to E D du Toit.

35 records · Page 2Linked to original sources
PubMed1989

Blood group gene frequencies of four population groups in the western Cape.

Blood group gene frequencies of 4 population groups in the western Cape region of South Africa were determined. The ABO, MNSs, Rhesus, Kell and Duffy blood group systems were studied in 2,094 non-Malay Cape Coloureds, 1,181 South African (SA) Negroes, 506 SA Caucasoids and 115 Cape Malays. The gene frequencies of these 4 population groups together with, for comparative purposes, previously published data on 3 others, namely Johannesburg Coloureds, Khoikhoi and San, were used to measure the genetic distances between them. In addition, multivariate analysis was used in an attempt to clarify whether the 2 coloured and the Cape Malay samples resemble each other, and to demonstrate the relationships between the 7 population groups. Although genetic distance measurements suggest that Johannesburg Coloureds have a greater SA Negro contribution to their gene pool than the Cape Coloureds, the results are in accordance with previous studies suggesting that coloureds in southern Africa form a relatively homogeneous group. The allele frequencies in the Rhesus and Duffy blood group systems suggest that Cape Malays, although similar in some respects to the Cape Coloureds, are a genetically distinct group.

ABO Blood-Group System↗
PubMed1989

HLA frequencies in the Indian population of Johannesburg.

The HLA class I antigen and haplotype frequencies of the three major Indian groups resident in the Johannesburg area, i.e. Hindus, Muslims and Tamils, were determined. The HLA-A, B and C antigens were tested in 460 healthy individuals. There were striking differences in antigen and haplotype frequencies between the various groups. Of interest was the finding of a complete lack of Aw34 in any of these groups. Although different haplotype frequencies appeared prominent in the different groups, all three groups demonstrated the haplotypes Aw33, B44, B35, Cw4 and B7, Cw7 in linkage disequilibrium. The results indicate dissimilarities between the various groups, underscoring the fact that use of these analyses is essential for the various applications of HLA testing.

Gene Frequency↗
PubMed1989

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.

Arthritis, Rheumatoid↗
PubMed1989

Paternity exclusion using 18 genetic systems in 2124 cases in four South African population groups.

Using 18 different blood group systems, 2,124 cases of doubtful paternity, unevenly distributed among four different population groups--South African Negroes (Xhosas) 645 (30%); South African Caucasians 264 (13%); Cape Coloureds (non-Malay) 1,156 (54%), and Cape Malays 59 (3%)--were analysed. Tests for red cell antigen, plasma protein, red cell enzyme and HLA polymorphisms were done on all subjects. The overall exclusion rate was 38,23%, i.e. 812 of the 2,124 men were not biological fathers of the children ascribed to them. The capability of the individual systems to exclude a man from specific paternity was also evaluated. The polymorphic HLA system was the most useful and alone--depending on the particular population group--excluded between 93.5% and 97.8% of falsely accused men. The proportion of men excluded also varied between different population groups using the different systems, e.g. the Rhesus system alone excluded 43.9% of South African Caucasian non-fathers and only 14% of the Xhosa non-fathers. This is a reflection of the gene frequencies within a particular population. The analysis showed that the genetic systems tested in this laboratory were extremely efficient in providing evidence in proof of non-paternity.

Black People↗
PubMed1989

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.

Alleles↗
PubMed1989

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.

Alleles↗
PubMed1989

HLA-Dw 'RSH': a new HLA-Dw specificity associated with HLA-DRw18(3).

The present study describes a new HLA-Dw specificity, Dw'RSH'. HLA-Dw'RSH' is associated with DRw18(3) and is clearly different to the DRw17(3) associated specificity Dw3. Dw'RSH' was shown to be the most common Dw specificity found in the South African (SA) Negroes (gf = 0.10) and was less common in Cape Coloureds (gf = 0.01). The specificity was absent in the SA Caucasoids tested. Dw'RSH' is part of the common Negro haplotype Bw42, DRw18, DQw4 which is seen as commonly in the SA Negroes as the B8, DRw17, DQw2, Dw3 haplotype is seen in the Caucasoids.

Black People↗
PubMed1988

HLA-A,B,C, and DR antigens, GLO I and Bf marker profiles in 75 Cape coloured patients with systemic lupus erythematosus (SLE).

HLA-A,B,C and DR antigens were tested in 75 Cape Coloured systemic lupus erythematosus (SLE) patients, and the GLO I and Bf markers in 51. The patients with HLA-DR2 had a relative risk significantly greater than one (p=0.0005). Twenty-two (29%) patients had only one detectable DR antigen. Of these, 11 (50%) were found to have DR2 only. The HLA-DR7 antigen was associated with severe disease (p less than 0.02). Bf and GLO I markers were not associated with SLE.

Complement Factor B↗
PubMed1988

Lack of an association between carcinoma of the stomach and the major histocompatibility complex (HLA) in Cape Coloureds.

A possible genetic contribution to the high incidence of gastric carcinoma in the Cape Coloured population of the Western Cape region of South Africa was investigated. The HLA-A, B, C, DR and DQ antigens were determined with a microcytotoxicity assay, and their frequencies compared in 124 individuals with gastric carcinoma and 4,560 controls. No significant difference was found, thus supporting the view that a genetic component has a minor, if any, role in gastric carcinogenesis.

Black People↗
PubMed1988

HLA-A, B, C, DR and DQ polymorphisms in three South African population groups: South African Negroes, Cape Coloureds and South African Caucasoids.

The HLA class I and II phenotypes of the three population groups in the Cape Province of South Africa were determined. The HLA-A,B, and C antigens were tested in 1027 South African Negroes (Xhosa), 3716 Cape Coloureds and 1059 South African Caucasoids. This is the first study which has also included the class II antigens in the Southern African Negroes (Xhosa). The numbers tested for the DR and DQ antigens were smaller, as only typings done after the 8th Histocompatibility Workshop were included. A comparison was made between the frequencies in the Xhosa, the Cape Coloureds and the South African Caucasoids as well as the Nigerians, another group who also belong to the Bantu-speaking division of African Negroes and who were recently studied. The antigen, gene and haplotype frequencies were estimated in all three groups, and the genetic distances calculated. Striking differences in gene and haplotype frequencies between the various populations were seen. For example, Bw42 had a phenotype frequency of 0.062 in the Cape Coloureds, 0.213 in the Xhosa and 0.004 in the South African Caucasoids. The Xhosa showed marked differences in HLA distribution compared to the other Negro group (Nigerians), which can be attributed to a Khoisan admixture, e.g. HLA-DR4 had a phenotype frequency of 0.134 in the Xhosa and only 0.010 in the Nigerians. The haplotype B8,DR3, seen in association with many autoimmune diseases, had a significant delta value in all three populations.

Black People↗
PubMed1987

The HLA linked iron loading gene in an Afrikaner population.

The serum ferritin concentration was used as a screening test to identify the presence of iron overload in 599 Afrikaans subjects (300 males and 299 females) living in the South Western Cape, South Africa. Seventeen of the males with concentrations greater than 400 micrograms/l were reevaluated three and five years later. Serum ferritin concentrations were measured again and further diagnostic procedures were carried out. These included an assessment of alcohol intake and measurements of serum gamma glutamyltransferase, the percentage saturation of transferrin, and HLA-A,-B,-C, and -DR loci typing on the subjects as well as their families. Liver biopsies were performed on some affected subjects. Of the original 16 index subjects, four were diagnosed as homozygous for the HLA linked iron loading gene which is responsible for the clinical disease idiopathic haemochromatosis. Six appeared to be heterozygotes, three were heterozygotes who were also abusing alcohol, and two did not fit into any of the diagnostic groups. The calculated gene frequency was 0.082, with an expected heterozygote frequency of 0.148. The fact that no females were identified in the study suggested that the diagnostic criteria for homozygosity (serum ferritin greater than 400 micrograms/l and % saturation greater than 60%) were set too high. The data were therefore recalculated for the 300 males; when this was done the gene frequency was 0.115 and the heterozygote frequency 0.024. Two subjects were diagnosed as homozygotes in the study of family members and 37 as heterozygotes (33 definite and four probable). Both the homozygotes and nine of the heterozygotes showed mild to moderate disturbances of iron metabolism. There was considerable overlap between the phenotype expression in these nine heterozygotes and the homozygotes, probably as a result of setting the threshold for the serum ferritin concentrations at the relatively high value of 400 microgram/ml. By doing this a small subset of heterozygotes with biochemical abnormalities was identified. The results of the present pilot study suggest a high frequency of the HLA linked iron loading gene in the Afrikaner population of South Western Cape.

Adolescent↗
PubMed1986

A study of the HLA-Dw determinants and their relationship to DR and DQ antigens in three South African population groups: South African Caucasoids, South African Negroes, and Cape coloureds.

The HLA-Dw specificities of a group of 177 unrelated randomly selected healthy individuals consisting of 67 South African Negroes (Xhosa), 57 Cape Coloureds, and 53 South African Caucasoids were determined. HLA-Dw specificities were determined in a mixed lymphocyte culture test using HTCs. Antigen and gene frequencies as well as the association between HLA-DR, DQ, and Dw were established in three populations. HLA-Dw gene frequencies in the South African Caucasoids agreed with these frequencies in other Caucasoid groups. The HLA-Dw1 frequency was decreased in the Cape Coloureds and South African Negroes compared to the Caucasoids. The gene frequency of Dw3 was low in the South African Negroes in spite of the fact that DR3 is a common DR antigen in this group. A high frequency of Dw 'blank' was observed in the South African Negroes and Cape Coloureds, suggesting the existence of undefined HLA-Dw specificities in these populations. Data concerning the HLA-Dw, DR, and DQ relationships showed that once a certain Dw specificity was associated with a particular DR and DQ antigen, this association remained a fixed entity in the different population groups.

Black People↗
PubMed1975

Utilization of iron dextran in recurrent iron deficiency anaemia.

Previously published studies have documented a reduction in the rate at which iron stores laid down by iron dextran therapy can be utilized for haemoglobin synthesis after the acute demands of haemorrhage and phlebotomy. In order to determine if a defect in the mobilization of these stores exists in the face of a chronic stimulus to red cell production, 93 patients who had previously received a total dose infusion of iron dextran were examined for a recurrence of iron deficiency anaemia, and in those in whom anaemia had recurred, iron stores were assessed by marrow aspiration. Twenty of the 93 patients were found to have recurrent iron deficiency anaemia, and marrow aspiration in all failed to demonstrate stainable iron stores. Although the rate at which iron dextran can be mobilized from storage sites is reduced, the present study demonstrates that ultimately these stores are fully utilizable.

Anemia, Hypochromic↗