The frequency of alpha+-thalassaemia, but not other unlinked DNA polymorphisms, exhibits an altitude- and latitude-dependent correlation with malaria endemicity throughout Melanesia, supporting the hypothesis that protection against this parasitic disease is the major factor responsible for the high frequencies of haemoglobinopathies in many parts of the world.

No abstract

The relative distributions of 480 DR2-related DR,DQ haplotypes have been determined in Australian Aborigines, Papua New Guinean Highlanders, coastal Melanesians, Micronesians, Polynesians, Javanese, and Southern and Northern Chinese. Using sequence-specific oligonucleotides (SSOs) for hybridization of polymerase chain reaction (PCR) products from DRB1, DRB5, DQA1, and DQB1 genes, 15 different DR2-related haplotypes were identified. The predominant DR2 haplotype in Oceania involved a novel combination of DRB1*1502, DRB5*0101 alleles; this haplotype occurred sporadically in Java, but not in China. In Southern China, the most frequent DR2 haplotype involved the unusual arrangement DRB1*1602,DRB5*0101; alternatively, DRB1*1602 was associated with a new DRB5 SSO pattern. This study has important implications for molecular HLA-typing protocols that assume particular DRB1, DRB5 or DR,DQ linkage relationships. Further, the novel DRB1, DRB5 haplotype in Oceania suggests that the mixed lymphocyte culture (MLC) determinants Dw2 and Dw12 are discriminated by codon 86 at the DRB1 locus.

Hereditary ovalocytosis in Papua New Guinea is restricted to areas of endemic malaria and may confer increased resistance to the disease. The incidence of malaria was investigated in 1616 Melanesiams of known red cell morphology and severity of infection determined in a smaller subsample. Ovalocytics tended to be more resistant to severe malarial infections than normocytics. The ratio of parasitaemia in 112 ovalocytics compared with 741 normocytic children was 1.05 for P. falciparum; 0.90 for P. vivax; 0.54 for P. malariae, and 0.91 for infection with any species. The difficulties in conclusively demonstrating any selective advantage of the condition are discussed.

No abstract

Recessively inherited ovalocytosis in coastal Melanesians is associated with widespread, but selective, depression of blood group antigens in homozygotes, who comprise about 15% of these populations. It is suggested that a membrane anomaly exists, and that the series of depressed determinants all depend, for their full expression, upon the same membrane component(s), the proper synthesis of which is being genetically affected. Affected antigens would thus be associated by position and/or structure. Antigens subject to depression include IT, IF, LW,D,C,e,S,s,U,Kpb,JKa,JKb,Xga,Wrb,Scl and Ena, which are simultaneously affected when present on oval cells. Reactivity of A1,ID,i,P1,M,N,Lub,k,Fya,Coa, Vel and Gea appears to be within the normal range on depressed cells, as does sialic acid content. Indirect evidence suggests that Z (associated with S and s) is among the depressed series, while NA and Leb are not. High H variants, common among Melanesians, seem absent among depressed bloods, and when such variants were excluded, H, A and B did not appear subject to depression. The distribution pattern of ovalocytosis suggests that it may confer some selective advantage in the tropical coastal environment. The findings also have implications concerning population genetic work in New Guinea.

Summary. Genetic factors play a major role in predisposition to diabetes in the Micronesian population of Nauru. In people aged 60years and older, 83% of full-blooded Nauruans were diabetic compared with 17% of those with ancestral foreign admixture, as detected by HLA typing. HLA distributions also showed a small increased risk for early onset of diabetes (< 46 years) associated with HLA-Bw22 (Bw56). Variation in the restriction fragment length of DNA near the insulin gene was found, but was not associated with diabetes. The distribution in fragment lengths, previously reported in Caucasoids, was observed in healthy Polynesians, Melanesians and Micronesians.

SUMMARY The synovial tissue and fluid of patients with rheumatoid arthritis (RA) contain activated T cells that probably have a central role in the disease process which leads to joint destruction. A subset of T cells, γδ T cells detected at the site of inflammation, may be important in the pathogenesis of the disease. This study investigated variable (V) gene usage of γδ T cell receptors (TcRs) expressed in synovia and peripheral blood of patients with RA by using the polymerase chain reaction (PCR) to amplify TcR γ‐and γ‐chain transcripts. Most patients showed no restriction in Vγ gene usage since synovial mononuclear cells (SMC) expressed TcR γ‐chain transcripts which used the same set of Vγ genes as peripheral blood mononuclear cells (PBMC). In contrast, the majority of patients expressed a restricted SMC Vδ‐chain repertoire biased towards Vδ1, but Vδ2 mRNA transcripts were also detected, albeit at low levels in some patients. The TcR δ‐chain repertoires of PBMC from healthy control subjects were also characterized. There was variation in the TcR δ‐chain repertoires of PBMC from patients when compared with controls, particularly with respect to expression of Vδ4. Vδ4 mRNA transcripts were expressed in PBMC of only two of seven RA patients in contrast with eight of the nine controls (P=0.03). These findings are compatible with reports that γδ T cells in the rheumatoid synovium are reactive to Mycobacterium tuberculosis and that response to M. tuberculosis is restricted to VγL9/Vδ2‐bearing T cells, if a superantigen is involved in the pathogenesis of RA.