How are antigens processed and presented?

Antigen processing and presentation is the process by which protein antigen is ingested by an antigen-presenting cell (APC), partially digested into peptide fragments and then displayed on the surface of the APC associated with an antigen-presenting molecule such as MHC class I or MHC class II, for recognition by …

How do antigens select their MHC?

Antigen Presentation with MHC II Molecules Proteases process bacterial antigens, and the most antigenic epitopes are selected and presented on the cell’s surface in conjunction with MHC II molecules. T cells recognize the presented antigens and are thus activated. MHC II molecules are only found on the surface of APCs.

What process is involved in the presentation of antigens from cytoplasmic pathogens on MHC class II molecules?

Autophagy promotes MHC class II presentation of peptides from intracellular source proteins.

What MHC do antigen-presenting cells have?

Antigen-presenting cells (APC) are cells that can process a protein antigen, break it into peptides, and present it in conjunction with class II MHC molecules on the cell surface where it may interact with appropriate T cell receptors.

How are antigens presented?

Antigens are presented by a set of cell surface proteins called major histocompatibility (MHC) proteins (Fig. 6.6). Their main function is to bind peptide fragments and display them on the cell surface for recognition by the appropriate T cells. MHC proteins bind and present both “self” and “foreign” peptides.

How are antigens processed?

Antigens derived from the cytoplasm (e.g., viral proteins) are processed by the endogenous pathway for presentation by MHC class I molecules (e.g., HLA-A, -B, -C) to CD8+ cells. The response to a hapten or drug is a function of the antigen processing pathway and is determined by its chemical properties.

How are peptides presented by MHC?

MHC class I molecules present a wide array of peptides to cytotoxic T lymphocytes, allowing the immune system to scan for intracellular pathogens and mutated proteins. They are translocated into the endoplasmic reticulum (ER) lumen by the peptide transporter TAP that has broad peptide specificity.

How are exogenous antigens processed and presented?

Exogenous proteins, however, are primarily presented by MHC-II molecules. Antigens are internalized by several pathways, including phagocytosis, macropinocytosis, and endocytosis, and eventually traffic to a mature or late endosomal compartment where they are processed and loaded onto MHC-II molecules.

How are antigen presenting macrophages created?

Sometimes a dendritic cell presents on the surface of other cells to induce an immune response, thus functioning as an antigen-presenting cell. Macrophages also function as APCs. After phagocytosis by APCs, the phagocytic vesicle fuses with an intracellular lysosome forming phagolysosome.

What would be an appropriate response if an antigen is presented on MHC class II molecules on B cells?

The process in which a lymphocyte’s antigen receptor binds to an antigen, allowing the lymphocyte to multiply. What would be an appropriate response if an antigen is presented on MHC class II molecules? An effector CD4 cell activates the presenting cell.