MHC and Antigen Presentation (Video Notes)

Vocabulary flashcards covering key MHC class I and II concepts, antigen processing, and related immunology terms from the video notes.

Neoantigen

A novel antigen generated by mutations or abnormal proteins (e.g., from viruses or tumor cells) that the immune system may recognize as non-self.

MHC class I

A cell-surface glycoprotein complex presenting endogenous peptides to CD8+ T cells; consists of an alpha chain (α1, α2, α3) and β2-microglobulin; peptide-binding groove formed by α1/α2.

CD8 T cell

A cytotoxic T lymphocyte that recognizes MHC I–peptide complexes via its TCR and kills infected or malignant cells.

Endogenous antigen

An antigen derived from within a cell, processed by the proteasome for MHC I presentation.

Alpha chain

The heavy chain of MHC class I that pairs with β2-microglobulin to form the complete molecule.

Alpha1 domain

The domain forming part of the peptide-binding groove in MHC I.

Alpha2 domain

The domain forming part of the peptide-binding groove in MHC I; works with α1 to bind peptides.

Alpha3 domain

The domain that anchors MHC I in the cell membrane and interacts with CD8.

Beta-2 microglobulin

The noncovalently bound light chain essential for proper folding and surface expression of MHC-I.

Peptide-binding groove

The cleft formed by α1 and α2 that binds the antigenic peptide for presentation.

Proteasome

The cytosolic protease complex that degrades proteins into peptides for MHC I.

TAP

Transporter associated with antigen processing; transports peptides into the rough ER for loading onto MHC I.

Rough ER

The endoplasmic reticulum site where peptide loading onto MHC I occurs.

Golgi apparatus

The organelle through which MHC I–peptide complexes traffic to the cell surface.

Cell surface expression

The display of MHC I on the cell membrane to present peptides to T cells.

Peptide presentation

The display of peptide–MHC complexes recognized by TCRs on T cells.

Self antigen

Peptides derived from the body's own proteins; normally tolerated.

Viral antigen

Peptides derived from viruses; can be presented by MHC I to CD8 T cells.

Tumor antigen

Peptides derived from tumor proteins; may include neoantigens recognized by T cells.

TCR

T cell receptor; antigen-specific receptor on T cells that recognizes peptide–MHC.

CD3 complex

The signaling complex associated with the TCR essential for T cell activation.

Endosome

Vesicular compartment where exogenous antigens are processed for MHC II loading.

Exogenous antigen

Antigen from outside the cell; processed for MHC II presentation.

MHC class II

A cell-surface glycoprotein complex presenting extracellular peptides to CD4+ T cells; composed of α and β chains.

Invariant chain (Ii)

Chaperone that blocks the MHC II peptide-binding groove in the ER to prevent premature binding.

CLIP

The placeholder peptide derived from Ii that sits in the MHC II groove until peptide loading.

Endosomal peptide loading

The process of loading processed extracellular peptides onto MHC II within endosomes after Ii removal.

HLA-DP

A human MHC class II molecule presenting extracellular peptides.

HLA-DQ

Another human MHC class II molecule presenting extracellular peptides.

HLA-DR

A major human MHC class II molecule presenting extracellular peptides.

HLA-DM

Regulator that facilitates exchange of CLIP for high-affinity peptides in endosomes.

HLA-DO

Regulator of HLA-DM function in peptide loading.

HLA-E

A nonclassical class I molecule with limited polymorphism, involved in NK cell interactions.

HLA-F

A nonclassical class I molecule with regulatory roles; less well understood.

HLA-G

A nonclassical class I molecule expressed on placental trophoblasts; inhibits maternal NK cell responses to prevent fetal rejection.

Placental tolerance (HLA-G)

In pregnancy, HLA-G signals to maternal NK cells to protect the fetus from attack.

Graft rejection

Immune rejection of transplanted tissue due to MHC incompatibility, driven by T cells recognizing donor MHC.