Summary
Surface proteins that display peptide fragments to T cells, distinguishing self from non-self.
In depth
MHC class I (all nucleated cells) presents endogenous peptides to CD8 T cells; class II (antigen presenting cells) presents exogenous peptides to CD4 cells. Very polymorphic genes (HLA in humans) give population diversity and matter for transplants.
MHC polymorphism means individuals present different peptides, so a pathogen can't escape everyone. Matching HLA types is crucial in transplants.
Key idea: T cells see antigen only when it's displayed on MHC.
MHC genes (HLA in humans, on chromosome 6) are the most polymorphic in the genome, with thousands of alleles, so populations show wide diversity in peptides presented, which resists pathogens. Each person has up to six class I and several class II types. Peptide loading uses TAP transporters (class I) and invariant chain and HLA-DM (class II). Viruses such as herpes and CMV interfere with MHC I presentation.
HLA type affects transplant matching and disease risk: HLA-B27 with ankylosing spondylitis, HLA-DR3 and DR4 with type 1 diabetes, and HLA-B*57:01 with abacavir hypersensitivity (tested before treatment). Mate choice experiments in mice and humans suggest preference for dissimilar MHC.
Key idea: MHC molecules are the display cases through which T cells inspect the inside of cells.
Frequently asked questions
What is MHC Molecules?
Surface proteins that display peptide fragments to T cells, distinguishing self from non-self.
Which area of biology covers MHC Molecules, and how advanced is it?
MHC Molecules is one of the 52 topics in Immunology & Disease. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Antigens, Antigenic Variation, Immunodeficiency.
Can you give an example of MHC Molecules?
HLA-B27 is associated with ankylosing spondylitis.
What should I learn before MHC Molecules?
Work through the Beginner topics in Immunology & Disease first, such as Immune System, Viruses, Innate Immunity, then return to MHC Molecules. Intermediate topics assume the Beginner vocabulary.
What topics are related to MHC Molecules?
The closest topics to MHC Molecules are Antigens, Antigenic Variation, Immunodeficiency, Bacterial vs Viral Infections. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand MHC Molecules?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for MHC Molecules. To practise the whole of Immunology & Disease, use the Immunology & Disease quiz.
How is MHC Molecules different from Antigens?
MHC Molecules: Surface proteins that display peptide fragments to T cells, distinguishing self from non-self. Antigens: Molecules, usually on pathogens, that trigger an immune response. Read both side by side and note what each one explains.
How should I study MHC Molecules step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Antigens and explain the difference aloud. Finally, take the Immunology & Disease quiz and come back to this page for any question you miss.