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An illustration that shows how antigens induce the immune system response by interacting with an antibody that matches the molecular structure of an antigen. In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. [1]
Antigen presentation stimulates immature T cells to become either mature "cytotoxic" CD8+ cells or mature "helper" CD4+ cells. An antigen-presenting cell (APC) or accessory cell is a cell that displays an antigen bound by major histocompatibility complex (MHC) proteins on its surface; this process is known as antigen presentation.
This antigen presentation pathway enables the immune system to detect transformed or infected cells displaying peptides from modified-self (mutated) or foreign proteins. [ 5 ] [ 6 ] In the presentation process, these proteins are mainly degraded into small peptides by cytosolic proteases in the proteasome , but there are also other cytoplasmic ...
The antigen is processed and presented on the B cell's surface again by MHC-II proteins. The MHC-II proteins are recognized by helper T cells, stimulating the production of proteins, allowing for B cells to multiply and the descendants to differentiate into antibody-secreting cells circulating in the blood. [8]
An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells.The part of an antibody that binds to the epitope is called a paratope.
After antigen peptide loading, the MHC molecule is transported out of the ER, through the Golgi complex, and then onto the cell surface for cross presentation. [10] It appears that both pathways are able to occur within an antigen presenting cell, and may be influenced by environmental factors such as proteasome and phagocytic inhibitors. [6]
BCRs bind intact antigens (like diphtheria toxoid, the protein introduced in the diphtheria-tetanus-pertussis vaccine). These may be soluble molecules present in the extracellular fluid; or intact molecules that the B cell plucks from the surface of antigen-presenting cells like macrophages and dendritic cells.
Immunocytochemistry labels individual proteins within cells, such as TH (green) in the axons of sympathetic autonomic neurons.. Immunocytochemistry (ICC) is a common laboratory technique that is used to anatomically visualize the localization of a specific protein or antigen in cells by use of a specific primary antibody that binds to it.