MHC class I

class IMHC Iclass I MHCMHCIMHC-Iclassclass 1 MHCclass I moleculeshistocompatibility antigens class iMajor Histocompatibility Class I (MHCI)
MHC class I molecules are one of two primary classes of major histocompatibility complex (MHC) molecules (the other being MHC class II) and are found on the cell surface of all nucleated cells in the bodies of jawed vertebrates.wikipedia
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Major histocompatibility complex

MHCmajor histocompatibility complex (MHC)HLA loci
MHC class I molecules are one of two primary classes of major histocompatibility complex (MHC) molecules (the other being MHC class II) and are found on the cell surface of all nucleated cells in the bodies of jawed vertebrates.
The MHC gene family is divided into three subgroups: MHC class I, MHC class II, and MHC class III.

MHC class II

MHC IIclass IIHLA class II
MHC class I molecules are one of two primary classes of major histocompatibility complex (MHC) molecules (the other being MHC class II) and are found on the cell surface of all nucleated cells in the bodies of jawed vertebrates.
The antigens presented by class II peptides are derived from extracellular proteins (not cytosolic as in MHC class I).

HLA-A

HLA-serotype tutorialAhla-a antigens
In humans, the HLAs corresponding to MHC class I are HLA-A, HLA-B, and HLA-C.
HLA-A is one of three major types of human MHC class I cell surface receptors.

Human leukocyte antigen

HLAhuman leukocyte antigenshuman leukocyte antigen (HLA)
In humans, the HLAs corresponding to MHC class I are HLA-A, HLA-B, and HLA-C.
HLAs corresponding to MHC class I (A, B, and C) which all are the HLA Class1 group present peptides from inside the cell.

HLA-B

Bhla-b antigensHLA-B*5701
In humans, the HLAs corresponding to MHC class I are HLA-A, HLA-B, and HLA-C.
Genes in this complex are separated into three basic groups: class I, class II, and class III.

Cross-presentation

[20] cross-primingcrosspresentation
However, class I MHC can also present peptides generated from exogenous proteins, in a process known as cross-presentation.
Cross-presentation is the ability of certain antigen-presenting cells to take up, process and present extracellular antigens with MHC class I molecules to CD8 T cells (cytotoxic T cells).

HLA-C

Chla-c antigensHLA-C554
In humans, the HLAs corresponding to MHC class I are HLA-A, HLA-B, and HLA-C.
HLA-C belongs to the MHC (human = HLA) class I heavy chain receptors.

Cytotoxic T cell

cytotoxic T cellsCD8+cytotoxic T lymphocytes
Their function is to display peptide fragments of proteins from within the cell to cytotoxic T cells; this will trigger an immediate response from the immune system against a particular non-self antigen displayed with the help of an MHC class I protein.
Antigens inside a cell are bound to class I MHC molecules, and brought to the surface of the cell by the class I MHC molecule, where they can be recognized by the T cell.

T cell

T cellsT-cellT-cells
The α 3 domain is plasma membrane-spanning and interacts with the CD8 co-receptor of T-cells.
These cells recognize their targets by binding to short peptides (8-11AA) associated with MHC class I molecules, present on the surface of all nucleated cells.

Peptide loading complex

The peptide-loading process involves several other molecules that form a large multimeric complex called the Peptide loading complex consisting of TAP, tapasin, calreticulin, calnexin, and Erp57 (PDIA3).
It orchestrates peptide translocation and selection by major histocompatibility complex class I (MHC-I) molecules.

Transporter associated with antigen processing

TAPTAP transporter
The peptide translocation from the cytosol into the lumen of the ER is accomplished by the transporter associated with antigen processing (TAP).
It delivers cytosolic peptides into the endoplasmic reticulum (ER), where they bind to nascent MHC class I molecules.

Tapasin

TAPBPtapapsin
The peptide-loading process involves several other molecules that form a large multimeric complex called the Peptide loading complex consisting of TAP, tapasin, calreticulin, calnexin, and Erp57 (PDIA3).
This gene encodes a transmembrane glycoprotein that mediates interaction between newly assembled major histocompatibility complex (MHC) class I molecules and the transporter associated with antigen processing (TAP), which is required for the transport of antigenic peptides across the endoplasmic reticulum membrane.

Calreticulin

CALRAutoantigen RoCRT
The peptide-loading process involves several other molecules that form a large multimeric complex called the Peptide loading complex consisting of TAP, tapasin, calreticulin, calnexin, and Erp57 (PDIA3).
Calreticulin and calnexin are also integral proteins in the production of MHC class I Proteins.

T-cell receptor

T cell receptorTCRT-cell receptors
The α 3 -CD8 interaction holds the MHC I molecule in place while the T cell receptor (TCR) on the surface of the cytotoxic T cell binds its α 1 -α 2 heterodimer ligand, and checks the coupled peptide for antigenicity.
Each T cell expresses clonal TCRs which recognize a specific peptide loaded on a MHC molecule (pMHC), either on MHC class II on the surface of antigen presenting cells or MHC class I on any other cell type.

HLA-E

Human Leukocyte Antigen (HLA)-E
The human HLA-E is a non-classical MHC class I molecule that is characterized by a limited polymorphism and a lower cell surface expression than its classical paralogues.

Natural killer cell

NK cellsnatural killer cellsNK cell
Alternatively, class I MHC itself can serve as an inhibitory ligand for natural killer cells (NKs).
The inhibitory receptors recognize MHC class I alleles, which could explain why NK cells preferentially kill cells that possess low levels of MHC class I molecules.

Calnexin

CANXCNX
The peptide-loading process involves several other molecules that form a large multimeric complex called the Peptide loading complex consisting of TAP, tapasin, calreticulin, calnexin, and Erp57 (PDIA3).
Calnexin associates with the protein folding enzyme ERp57 to catalyze glycoprotein specific disulfide bond formation and also functions as a chaperone for the folding of MHC class I α-chain in the membrane of the ER.

HLA-G

HLA-G may play a role in immune tolerance in pregnancy, being expressed in the placenta by extravillous trophoblast cells (EVT), while the classical MHC class I genes (HLA-A and HLA-B) are not.

Cell membrane

plasma membranemembranecell membranes
MHC class I molecules are one of two primary classes of major histocompatibility complex (MHC) molecules (the other being MHC class II) and are found on the cell surface of all nucleated cells in the bodies of jawed vertebrates.

Cell nucleus

nucleusnucleinuclear
MHC class I molecules are one of two primary classes of major histocompatibility complex (MHC) molecules (the other being MHC class II) and are found on the cell surface of all nucleated cells in the bodies of jawed vertebrates.

Vertebrate

Vertebratavertebratesvertebral
MHC class I molecules are one of two primary classes of major histocompatibility complex (MHC) molecules (the other being MHC class II) and are found on the cell surface of all nucleated cells in the bodies of jawed vertebrates.

Platelet

plateletsplatelet aggregationplatelet count
They also occur on platelets, but not on red blood cells.

Red blood cell

red blood cellserythrocyteserythroid
They also occur on platelets, but not on red blood cells.

Peptide

polypeptidepeptidespolypeptides
Because MHC class I molecules present peptides derived from cytosolic proteins, the pathway of MHC class I presentation is often called cytosolic or endogenous pathway.

Cytosol

cytosolichyaloplasmintracellular fluid
Because MHC class I molecules present peptides derived from cytosolic proteins, the pathway of MHC class I presentation is often called cytosolic or endogenous pathway.