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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Burkitt's lymphoma (BL) is a highly malignant B cell tumor characterized by three types of chromosomal translocation which constitutively activate the c-myc oncogene by juxtaposing it to Ig coding sequences. Epstein-Barr virus (EBV) infection, hyperendemic malaria and HIV-caused immunosuppression are thought to contribute to the pathogenesis of the tumor. Cell lines derived from EBV carrying and EBV negative BLs often show altered MHC class I antigen expression. The defects include a lower expression of all HLA class I antigens compared to EBV transformed normal B-blasts, and selective down-regulation of certain HLA-A and HLA-C alleles. As a consequence BL cells are often resistant to cytotoxic T lymphocyte (CTL) mediated destruction. Alleles selective down-regulations are found only in cell lines that maintain the tumor cell phenotype while shift towards a more activated 'B-blast like' phenotype is accompanied by HLA class I up-regulation. A similar pattern of HLA class I expression can be found in a subpopulation of germinal center B cells which express a 'BL like' phenotype. Our findings suggest that the HLA class I expression of BL cells reflects the characteristics of the normal B cell precursor and is probably not the result of immune selection.
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PMID:Cell phenotype dependent expression of MHC class I antigens in Burkitt's lymphoma cell lines. 165 15

HLA-A,B,C and DR types were determined for 46 adults living in the Madang area of Papua New Guinea. Sera from these individuals were tested by ELISA for antibodies against: (i) sonicated schizont extract of Plasmodium falciparum; (ii) circumsporozoite repeat regions of P. falciparum and P. vivax; and (iii) epitopes on the 230 and 48/45 kD gametocyte antigens of P. falciparum. All sera were from highly immune individuals and reacted strongly to the schizont antigen. The proportions responding to circumsporozoite repeat regions were 60.7% and 23.9% for P. falciparum and P. vivax, respectively. Between 32.6 and 47.8% of adults responded to each gametocyte epitope as assessed by inhibition of monoclonal antibodies. The limited number of alleles present at each HLA locus which is characteristic of coastal Papua New Guinea was observed. Five HLA-DR alleles were detected, of which only three (HLA-DR2, 4 and w5) were present at frequencies over 0.12. All individuals possessed at least one DR2,4 or w5 allele, and 96% of individuals possessed DR2, or 4 or both. There was no evidence for association between HLA type and antibody response to circumsporozoite repeat regions or the gametocyte epitopes. Homozygotes for DR2 and 4 were able to respond to each antigen. These results imply that either there is no HLA restriction of the response to these antigens or that each DR type is responding to a different variant of the T-epitope. Even in the latter case the results are encouraging for the prospects of inclusion of an HLA-restricted T-epitope in a malaria vaccine for Papua New Guinea since a limited number of versions would be required to cover a population with an HLA profile similar to that in Madang.
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PMID:Association between HLA type and antibody response to malaria sporozoite and gametocyte epitopes is not evident in immune Papua New Guineans. 248 46

Hyperreactive malarious splenomegaly (HMS) represents an abnormal immune response to recurrent malarial infection. In the Upper Watut Valley of Papua New Guinea, where over 80% of adult inhabitants are known to develop the disease, human leucocyte antigen (HLA) studies have demonstrated an association between the antigen DR2 and gross splenomegaly. To test the hypothesis that the magnitude of the individual immune response to malaria is also influenced by the number of different HLA antigens present, we have studied the correlation of the level of observed heterozygosity at HLA-A, -B, -C and -DR loci with the degree of splenomegaly in adult Watut subjects. Heterozygosity per se provides additional antigens for the formation of complexes between HLA and foreign antigenic epitopes, considered crucial to mounting an immune response. Multiply heterozygous individuals were found to exhibit more intense immune responses to recurrent malarial infections than did individuals with low multiple-locus heterozygosity. On the basis of the analysis presented here, we suggest that the degree of immune response to malaria is also influenced by the level of HLA heterozygosity, although the exact mechanisms remain unclear.
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PMID:HLA heterozygosity and hyperreactive malarious splenomegaly in the Upper Watut Valley of Papua New Guinea. 269 23

Human leucocyte antigens (HLA) were used as genetic markers in an attempt to determine possible host genetic susceptibility or resistance to malarial infections. HLA-A and B typing on lymphocytes from 68 confirmed P. falciparum and 77 P. vivax cases was compared with that found in 66 control subjects with no known history of malaria. A significant deviation was observed in the distribution of HLA-B27. This phenotype was absent in the P. falciparum group although found present in the P. vivax group (10%) and the control group (11%). Also, the combination of A9(w24) and B5 was significantly higher among the P. falciparum group than that found in the P. vivax and control groups. These findings require confirmation but do suggest the possibility of genetic susceptibility and that extensive genetic studies might be worth investigating.
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PMID:HLA antigens and malaria at San Lazaro Hospital Manila, Philippines. 637 12

Eighty-five patients with thalassemia and all available immediate family members were typed for HLA-A,B, C, and DR antigens, and the patients were tested for clinical diabetes and white cell antibodies in response to multiple blood transfusions. The antigen Bw35 was increased among both patients and their parents. This finding is consistent with previous data suggesting that this antigen may offer an independent selective advantage in populations at risk for both thalassemia and malaria. No association of the HLA system to the development of diabetes was noted. A wide variation was observed in the degree of white cell antibody response to transfusions: 25 of the 84 patients tested had significant levels of white cell antibodies while the majority (49) of the patients had essentially no antibodies. The frequency of the antigen DR2 was significantly increased in the high-response group, while the antigens Bw35 and DR7 were significantly increased in the low-response group. This finding suggests that an HLA-linked immune response or immune suppression factor or an HLA-linked susceptibility to iron toxicity may play a role in the development of these antibody responses.
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PMID:HLA-A, B, C, and DR antigen frequencies in relation to development of diabetes and variations in white cell antibody formation in highly transfused thalassemia patients. 695 55

Association and linkage studies have established the importance of the major histocompatibility complex (MHC) in the susceptibility for multiple sclerosis (MS). We carried out a case-control study to investigate the ancestral haplotype A30B18DR3 and MS in the Nuoro population of Sardinia, which is isolated and genetically distinct from other populations in the Mediterranean basin and characterized by genetic homogeneity, high level of inbreeding, low migration, high prevalence of MS, high frequency of the relevant haplotype, and high past malaria prevalence. Cases and controls were serologically typed for the currently recognized HLA-A, B, and DR antigens. We used a log-linear approach to fit a wide class of models. We tested our hypothesis comparing different models via a likelihood ratio test. We overcame the complication due to unknown gametic phase using expectation-maximization (EM) algorithm as the estimation method. We estimated confidence intervals for odds ratio by using a profile likelihood approach. We found that: (1) the ancestral haplotype A30B18DR3 was associated to MS after allowing for a possible stratification in cases and controls; (2) DR3 allele was conditional independent on disease status, given A30B18 haplotype; (3) there was a tendency for ORs for the high-risk haplotypes to be higher in the high malaria strata; however, this indication did not achieve statistical significance (P = 0.11).
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PMID:Association between the ancestral haplotype HLA A30B18DR3 and multiple sclerosis in central Sardinia. 1118 Apr 52

Frank Livingstone played a central role in defining the population genetics of the sickle cell mutation at position 6 of the human beta globin gene, the most famous amino acid substitution in evolutionary biology. Its discovery occurred at a time when traditional, 19th-century principles of natural selection were being joined with the newly discovered mechanics of DNA structure and protein synthesis to produce Neo-Darwinian theory. When combined with the epidemiology of malaria in Africa, differential mortality for both homozygotes, and the resulting advantage of the heterozygote, sickle cell became the classic balanced polymorphism. Human HLA-A has 237 molecular alleles. The histocompatibility system has as its primary function the presentation of peptides to T-cell receptors and plays an essential role in the immune system. Nearly all of the alleles are codominant and fully functional. Despite almost 30 years of disease-association studies with HLA-A, no convincing evidence has been found for differential fertility or mortality at this locus. Yet the dogma in the histocompatibility field is that this extensive human polymorphism is maintained by "balancing selection." Explaining HLA-A polymorphism is what one might call the sickle-cell-effect. This one mutation, coming as it did at the historical convergence of Darwinian theory and modern genetics, and carrying with it the strong relationship between mutation, disease, and allele frequency, has conditioned our discussion of human genetic variation and population genetics. Has the strength of this early idea made evolutionary biologists uncritical of systems like HLA-A and retarded the search for new mechanisms of molecular evolution? Is it now time to move away from a focus on mutation and polymorphism in evolutionary genetics and toward a systems theory that would explain the origin and evolution of hemoglobin and HLA-A and the biochemical pathways that surround them?
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PMID:The mind of primitive anthropologists: hemoglobin and HLA, patterns of molecular evolution. 1465 78

HLA class-I and class-II allele frequencies and two-locus haplotypes were examined in 367 unrelated Melanesians living on the islands of Vanuatu and New Caledonia. Diversity at all HLA class-I and class-II loci was relatively limited. In class-I loci, three HLA-A allelic groups (HLA-A*24, HLA-A*34 and HLA-A*11), seven HLA-B alleles or allelic groups (HLA-B*1506, HLA-B*5602, HLA-B*13, HLA-B*5601, HLA-B*4001, HLA-B*4002 and HLA-B*2704) and four HLA-C alleles or allelic groups (HLA-Cw*04, HLA-Cw*01, HLA-Cw*0702 and HLA-Cw*15) constituted more than 90% of the alleles observed. In the class-II loci, four HLA-DRB1 alleles (HLA-DRB1*15, HLA-DRB1*11, HLA-DRB1*04 and HLA-DRB1*16), three HLA-DRB3-5 alleles (HLA-DRB3*02, HLA-DRB4*01 and HLA-DRB5*01/02) and five HLA-DQB1 alleles (HLA-DQB1*0301, HLA-DQB1*04, HLA-DQB1*05, HLA-DQB1*0601 and HLA-DQB1*0602) constituted over 93, 97 and 98% of the alleles observed, respectively. Homozygosity showed significant departures from expected levels for neutrality based on allele frequency (i.e. excess diversity) at the HLA-B, HLA-Cw, HLA-DQB1 and HLA-DRB3/5 loci on some islands. The locus with the strongest departure from neutrality was HLA-DQB1, homozygosity being significantly lower than expected on all islands except New Caledonia. No consistent pattern was demonstrated for any HLA locus in relation to malaria endemicity.
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PMID:HLA class-I and class-II allele frequencies and two-locus haplotypes in Melanesians of Vanuatu and New Caledonia. 1554 41

Several associations between specific HLA alleles and susceptibility or resistance to Plasmodium falciparum malaria have been previously reported, but no associations have been confirmed in multiple populations. We studied associations between HLA-A, -B, and DRB1 alleles and severe malaria in northern Ghana. We analyzed HLA-DRB1*04 in 4,032 subjects from a severe malaria case-control study, 790 severe malaria cases, 1,611 mild malaria controls, and 1631 asymptomatic controls. The presence of HLA-DRB1*04 was associated with severe malaria (OR = 2.42, 95% CI = 1.64, 3.58). The allele frequency of DRB1*04 was similar in the two major ethnic groups in the study population, Kassem (4.4%) and Nankam (4.7%), and the OR for the association between DRB1*04 and severe malaria was similar in both ethnic groups. These findings are consistent with results from Gabon suggesting that DRB1*04 is a risk factor for severe malaria.
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PMID:HLA-DRB1*04 allele is associated with severe malaria in northern Ghana. 1825 25

The objective of this study was to characterize the class I human leukocyte antigen (HLA) genetic composition of the Ugandan population to better define its relationship with other African groups. Samples from 175 individuals from Kampala (Uganda) were subjected to class I HLA-A, -B, and -C sequence-based typing. The high concordance between the major alleles and haplotypes found in the current and Kenyan populations and interpopulation genetic distance analysis strongly supported the presence of an East African cluster that contained the current Ugandan population along with Kenyan Luo and Nandi populations. The congruence of major alleles in different populations would permit consideration of East Africa as an integrated setting when designing and evaluating much needed malaria, tuberculosis, and AIDS vaccines.
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PMID:HLA class I allele and haplotype diversity in Ugandans supports the presence of a major east African genetic cluster. 1925 58


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