Major Histocompatibility Complex and Antigen Presentation

Vocabulary flashcards covering the concepts, molecules, pathways, and cell types involved in MHC antigen presentation based on the lecture.

Innate immune response

An immediate and non-specific immune defense mechanism.

Adaptive immune response

A delayed and specific immune response carried out by unique B cells and T-cells.

Antigens

Unique parts of pathogens, typically short peptides when presented to T-cells, that are specifically recognized by B cells and T-cells.

Major histocompatibility complex (MHC)

Cell-surface proteins, also called human leukocyte antigens (HLA), encoded by genes on chromosome $6$ that display peptide antigens to T-cells.

MHC class $1$ genes

A group of genes on chromosome $6$ that encode single-letter named proteins (HLA-A, HLA-B, and HLA-C) bound by CD$8$ molecules on cytotoxic T-cells.

MHC class $2$ genes

A group of genes on chromosome $6$ that encode two-letter named proteins (HLA-DP, HLA-DQ, and HLA-DR) bound by CD$4$ molecules on helper T-cells.

Mature erythrocytes

Red blood cells that lack a nucleus and are the only cells in the body that do not express MHC class $1$ molecules.

Antigen presenting cells

Specialized immune cells—monocytes, macrophages, dendritic cells, and B cells—that uniquely express MHC class $2$ molecules.

Beta $2$ microglobulin

A protein chain in the MHC class $1$ molecule that props up the structure by binding between the alpha $1$, alpha $2$, and alpha $3$ domains.

Endogenous pathway

The antigen presentation pathway used by MHC class $1$ molecules to process intracellular proteins and present them to CD$8$ positive cytotoxic lymphocytes.

Proteasome

An organelle found in all nucleated cells that degrades cellular proteins marked for degradation into short peptide chains.

Transporters associated with antigen processing (TAP)

Proteins that transport proteasome-degraded peptide chains into the endoplasmic reticulum for MHC class $1$ loading.

Tapasin

A molecule that facilitates the loading of short peptide chains into the peptide groove of the MHC class $1$ molecule inside the endoplasmic reticulum.

Exogenous pathway

The antigen presentation pathway used by MHC class $2$ molecules to ingest, process extracellular pathogens in vesicles, and present them to CD$4$ positive helper T-cells.

Invariant chain

A protein that temporarily fills the peptide binding groove of an MHC class $2$ molecule in the endoplasmic reticulum until it reaches a phagolysosomal vesicle.