Loiseau Claire, Zoorob Rima, Garnier Stéphane, Birard Julien, Federici Pierre, Julliard Romain, Sorci Gabriele
Laboratoire de Parasitologie Evolutive, CNRS UMR 7103, Université Pierre et Marie Curie, Bât. A, 7ème étage, 7, quai St Bernard, Case 237, F-75252 Paris Cedex 05, France.
Ecol Lett. 2008 Mar;11(3):258-65. doi: 10.1111/j.1461-0248.2007.01141.x. Epub 2007 Dec 7.
Genes of the Major Histocompatibility Complex (Mhc) play a fundamental role during the immune response because MHC molecules expressed on cell surface allow the recognition and presentation of antigenic peptides to T-lymphocytes. Although Mhc alleles have been found to correlate with pathogen resistance in several host-parasite systems, several studies have also reported associations between Mhc alleles and an accrued infection risk or an accelerated disease progression. The existence of these susceptibility alleles is puzzling, as the cost generated by the infection should rapidly eliminate them from the population. Here, we show that susceptibility alleles may be maintained in a population of house sparrows (Passer domesticus) if they have antagonistic effects on different malaria parasites. We found that one Mhc class I allele was associated with a 2.5-fold increase in the risk to be infected with a Plasmodium strain, but with a 6.4-fold reduction in the risk to harbour a Haemoproteus strain. We suggest that this antagonistic effect might arise because Mhc genes can alter the competitive interactions between malaria parasites within the host.
主要组织相容性复合体（Mhc）的基因在免疫反应中发挥着重要作用，因为细胞表面表达的Mhc分子能够识别并将抗原肽呈递给T淋巴细胞。尽管在多个宿主-寄生虫系统中已发现Mhc等位基因与病原体抗性相关，但也有多项研究报告了Mhc等位基因与感染风险增加或疾病进展加速之间的关联。这些易感性等位基因的存在令人费解，因为感染产生的代价应会迅速将它们从种群中淘汰。在此，我们表明，如果易感性等位基因对不同疟原虫具有拮抗作用，那么它们可能会在家麻雀（Passer domesticus）种群中得以维持。我们发现，一个Mhc I类等位基因与感染一种疟原虫菌株的风险增加2.5倍相关，但与感染血变原虫菌株的风险降低6.4倍相关。我们认为，这种拮抗作用可能是因为Mhc基因能够改变宿主体内疟原虫之间的竞争相互作用而产生的。
