Data from: Genes of the major histocompatibility complex highlight interactions of the innate and adaptive immune system

Background: A well-functioning immune defence is crucial for fitness, but
our knowledge about the immune system and its complex interactions is
still limited. Major histocompatibility complex (MHC) molecules are
involved in T-cell mediated adaptive immune responses, but MHC is also
highly upregulated during the initial innate immune response. The aim of
our study was therefore to determine to what extent the highly polymorphic
MHC is involved in interactions of the innate and adaptive immune defence
and if specific functional MHC alleles (FA) or heterozygosity at the MHC
are more important. Methods: To do this we used captive house sparrows
(Passer domesticus) to survey MHC diversity and immune function
controlling for several environmental factors. MHC class I alleles were
identified using parallel amplicon sequencing and to mirror immune
function, several immunological tests that correspond to the innate and
adaptive immunity were conducted. Results: Our results reveal that MHC was
linked to all immune tests, highlighting its importance for the immune
defence. While all innate responses were associated with one single FA,
adaptive responses (cell-mediated and humoral) were associated with
several different alleles. Discussion: We found that repeated injections
of an antibody in nestlings and adults were linked to different FA and
hence might affect different areas of the immune system. Also, individuals
with a higher number of different FA produced a smaller secondary
response, indicating a disadvantage of having numerous MHC alleles. These
results demonstrate the complexity of the immune system in relation to the
MHC and lay the foundation for other studies to further investigate this
topic.

研究背景：功能健全的免疫防御对于机体适合度至关重要，但目前学界对免疫系统及其复杂交互作用的认知仍较为有限。主要组织相容性复合体（Major Histocompatibility Complex, MHC）分子参与T细胞介导的适应性免疫应答，然而MHC在先天免疫应答初始阶段也会被高度上调。因此本研究旨在明确高度多态性的MHC在先天与适应性免疫防御交互过程中的参与程度，以及特异性功能等位基因（Functional Allele, FA）或MHC位点杂合性何者更为关键。研究方法：本研究以圈养家麻雀（Passer domesticus）为实验对象，在控制多种环境因素的前提下，对其MHC多样性与免疫功能开展调查。通过并行扩增子测序鉴定MHC I类等位基因，并开展多项对应先天免疫与适应性免疫的免疫学检测以表征免疫功能。研究结果：本研究结果显示，MHC与所有免疫检测指标均存在关联，凸显其在免疫防御中的重要性。所有先天免疫应答均与单一特异性功能等位基因相关联，而适应性免疫应答（包括细胞介导免疫与体液免疫）则与多种不同等位基因相关联。讨论：本研究发现，对雏鸟与成体重复注射抗体的操作与不同的特异性功能等位基因存在关联，因此该操作可能对免疫系统的不同区域产生影响。此外，携带不同特异性功能等位基因数量更多的个体，其二次免疫应答强度更低，这表明拥有大量MHC等位基因可能存在一定劣势。上述结果揭示了免疫系统与MHC之间关联的复杂性，同时也为后续相关研究奠定了基础。