Transmembrane Helices Are an Over-Presented and Evolutionarily Conserved Source of Major Histocompatibility Complex Class I and II Epitopes

Front Immunol. 2022 Jan 11:12:763044. doi: 10.3389/fimmu.2021.763044. eCollection 2021.


Cytolytic T cell responses are predicted to be biased towards membrane proteins. The peptide-binding grooves of most alleles of histocompatibility complex class I (MHC-I) are relatively hydrophobic, therefore peptide fragments derived from human transmembrane helices (TMHs) are predicted to be presented more often as would be expected based on their abundance in the proteome. However, the physiological reason of why membrane proteins might be over-presented is unclear. In this study, we show that the predicted over-presentation of TMH-derived peptides is general, as it is predicted for bacteria and viruses and for both MHC-I and MHC-II, and confirmed by re-analysis of epitope databases. Moreover, we show that TMHs are evolutionarily more conserved, because single nucleotide polymorphisms (SNPs) are present relatively less frequently in TMH-coding chromosomal regions compared to regions coding for extracellular and cytoplasmic protein regions. Thus, our findings suggest that both cytolytic and helper T cells are more tuned to respond to membrane proteins, because these are evolutionary more conserved. We speculate that TMHs are less prone to mutations that enable pathogens to evade T cell responses.

Keywords: MHC-I; MHC-II; adaptive immunity; antigen presentation; epitopes; evolutionary conservation; membrane proteins; transmembrane domain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Antigen Presentation / genetics*
  • Antigen Presentation / immunology
  • Chromosomes / genetics
  • Chromosomes / immunology
  • Cytoplasm / genetics
  • Cytoplasm / immunology
  • Epitopes, T-Lymphocyte / genetics*
  • Epitopes, T-Lymphocyte / immunology
  • Histocompatibility Antigens Class I / genetics*
  • Histocompatibility Antigens Class I / immunology
  • Histocompatibility Antigens Class II / genetics*
  • Histocompatibility Antigens Class II / immunology
  • Humans
  • Membrane Proteins / genetics*
  • Membrane Proteins / immunology
  • Peptides / genetics
  • Peptides / immunology
  • Polymorphism, Single Nucleotide / genetics
  • Polymorphism, Single Nucleotide / immunology
  • Protein Structure, Secondary / genetics*
  • T-Lymphocytes, Helper-Inducer / immunology


  • Epitopes, T-Lymphocyte
  • Histocompatibility Antigens Class I
  • Histocompatibility Antigens Class II
  • Membrane Proteins
  • Peptides