Major Histocompatibility Complex Diversity in Evolutionary Genetics

The Major Histocompatibility Complex (MHC) represents one of the most polymorphic regions in vertebrate genomes, central to antigen presentation and adaptive immunity. Diversity at MHC loci is maintained by a balance of evolutionary forces, notably pathogen-driven selection, heterozygote advantage and frequency-dependent interactions. These forces give rise to exceptionally high numbers of alleles within populations, with long coalescence times and trans-species polymorphisms evident across mammals, birds and fish. Geographic variation in pathogen communities, hybridisation events and introgression have further shaped MHC allelic repertoires, enhancing local adaptation. Advances in high-throughput sequencing and eco-evolutionary modelling have elucidated mechanisms underlying allele maintenance and turnover, revealing trade-offs between immunological breadth and autoimmunity risks. Understanding MHC diversity has profound implications for conservation genetics, disease ecology and the management of emerging zoonoses, as well as for vaccine design and transplantation biology.

Research from Nature Portfolio

Recent studies have examined the impact of human disturbance on MHC–pathogen co-evolution in a generalist rodent species across rainforest landscapes. In less disturbed habitats, rich functional associations between MHC class II alleles and diverse pathogens were maintained, whereas in heavily altered sites both genome-wide and adaptive MHC diversity declined. This loss corresponded with simplified immunogenetic-pathogen networks, suggesting that anthropogenic change can erode parasite-mediated selection and potentially facilitate spill-over events. The work underscores how landscape-level disturbance may reshape host immunogenetic landscapes, with direct relevance to zoonotic risk assessments and wildlife management.

Major Histocompatibility Complex Diversity in Evolutionary Genetics publication trend

The graph below shows the total number of articles in major histocompatibility complex diversity in evolutionary genetics across all publications each year (not limited to Nature Index journals).

Technical terms

Major Histocompatibility Complex (MHC): A genomic region encoding cell-surface proteins that present peptide antigens to T cells, critical for adaptive immunity.

Polymorphism: The presence of multiple genetic variants (alleles) at a particular locus within a population.

Heterozygote advantage: A form of balancing selection in which individuals carrying two different alleles at a locus have higher fitness than those with two identical alleles.

Balancing selection: An evolutionary process that maintains genetic diversity in a population through mechanisms such as heterozygote advantage, frequency-dependent selection and varying environmental pressures.

Peptide-binding domain: The region of an MHC molecule that binds and displays antigenic peptides for recognition by T-cell receptors.

References

1. Heterozygote advantage can explain the extraordinary diversity of immune genes. eLife (2024).
2. Ancient duplication, coevolution, and selection at the MHC class IIA and IIB genes of birds. Frontiers in Immunology (2023).
3. Immunogenetic-pathogen networks shrink in Tome’s spiny rat, a generalist rodent inhabiting disturbed landscapes. Communications Biology (2024).
4. Advances in the Evolutionary Understanding of MHC Polymorphism. Trends in Genetics (2020).