What is the Difference Between MHC I and II?
🆚 Go to Comparative Table 🆚Major Histocompatibility Complex (MHC) proteins are essential for adaptive immunity and are responsible for presenting antigens to the immune system. There are two major classes of MHC proteins: MHC Class I and MHC Class II. The main differences between them are:
- Structure and Composition: MHC Class I proteins are composed of a heavy chain (α chain) and a smaller non-covalently associated protein called β2-microglobulin, while MHC Class II proteins are composed of an α chain and a β chain.
- Peptide-binding Groove: MHC Class I molecules typically bind peptides of 8-11 amino acids, most commonly of 9 amino acids, within a closed groove formed by their membrane-distal domains. In contrast, MHC Class II molecules typically bind peptides of 12-25 amino acids that extend beyond the ends of their open groove.
- Cellular Distribution: MHC Class I proteins are present on almost all cells with a nucleus, while MHC Class II proteins have a more limited distribution and are typically found on dendritic cells, macrophages, and B cells.
- Antigen Sources: MHC Class I proteins present antigens derived from endogenous sources, such as cytosolic proteasome, while MHC Class II proteins present antigens derived from exogenous sources, processed by lysosomal and endosomal proteases.
- T Cell Recognition: MHC Class I proteins are recognized by the CD8+ receptor of cytotoxic T cells, while MHC Class II proteins are recognized by the CD4+ receptor of helper T cells.
In summary, MHC Class I and MHC Class II proteins differ in their structure, composition, cellular distribution, antigen sources, and T cell recognition. These differences enable them to present antigens to the immune system in distinct ways, contributing to the overall functioning of the immune response.
Comparative Table: MHC I vs II
MHC I and MHC II are two classes of molecules within the Major Histocompatibility Complex (MHC), which plays a crucial role in the immune system. Here is a table summarizing the differences between MHC I and MHC II:
Feature | MHC I | MHC II |
---|---|---|
Structure | Consists of one membrane-spanning α chain and one β chain | Consists of two membrane-spanning chains, α and β, of similar size |
Expressed by | Nearly all nucleated cells | Antigen-presenting cells (APCs) such as macrophages, dendritic cells, and B cells |
Antigen processing | Processes endogenous antigens (from within the cell) | Processes exogenous antigens (from outside the cell) |
Antigen presentation | Presents antigens to cytotoxic T cells | Presents antigens to helper T cells |
Disease association | MHC I alleles are associated with various Autoimmune diseases like multiple sclerosis, rheumatoid arthritis, and type 1 diabetes | MHC II alleles are associated with Autoimmune diseases like rheumatoid arthritis, type 1 diabetes, and multiple sclerosis |
The structural differences between MHC I and MHC II molecules result in different antigen processing and presentation pathways. MHC I presents endogenous antigens to cytotoxic T cells, while MHC II presents exogenous antigens to helper T cells.
- HLA vs MHC
- Major vs Minor Histocompatibility Antigens
- Type I vs Type II Interferon
- TH1 vs TH2 Helper Cells
- Meiosis I vs Meiosis II
- ICAM-1 vs VCAM-1
- HTLV 1 vs 2
- Interleukin 1 vs 2
- T Cells vs B Cells
- Immunocytochemistry vs Immunohistochemistry
- IgM vs IgG
- Memory T Cells vs Memory B Cells
- Macrophages vs Dendritic Cells
- T Helper vs T Cytotoxic Cells
- Innate vs Adaptive Immunity
- O vs H Antigen
- Type 1 vs Type 2 Alveolar Cells
- Immunofluorescence vs Immunohistochemistry
- Humoral vs Cell Mediated Immunity