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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]
Each antibody binds to a specific antigen in a highly specific interaction analogous to a lock and key.. An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that cause disease.
Antigen-presenting cells fall into two categories: professional and non-professional. Those that express MHC class II molecules along with co-stimulatory molecules and pattern recognition receptors are often called professional antigen-presenting cells. [1] The non-professional APCs express MHC class I molecules.
B-cell receptors on the surface of B cells bind to intact native and undigested antigens of a structural nature, rather than to a linear sequence of a peptide which has been digested into small fragments and presented by MHC molecules. Large complexes of intact antigen are presented in lymph nodes to B cells by follicular dendritic cells in the ...
In contrast, the B cell antigen-specific receptor is an antibody molecule on the B cell surface and recognizes native (unprocessed) antigen without any need for antigen processing. Such antigens may be large molecules found on the surfaces of pathogens, but can also be small haptens (such as penicillin) attached to carrier molecule. [60]
Later studies revealed that tissue rejection due to incompatibility is only a facet of the full function of MHC molecules, which is to bind an antigen derived from self-proteins, or from pathogens, and bring the antigen presentation to the cell surface for recognition by the appropriate T-cells. [2]
The unique variable region allows an antibody to recognize its matching antigen. [7] Most large molecules, including virtually all proteins and many polysaccharides, can serve as antigens. [3] The parts of an antigen that interact with an antibody molecule or a lymphocyte receptor, are called epitopes, or antigenic determinants
Even though, most classes of human pathogens are covered by CLRs, CLRs are a major receptor for recognition of fungi: [15] [16] nonetheless, other PAMPs have been identified in studies as targets of CLRs as well e.g. mannose is the recognition motif for many viruses, fungi and mycobacteria; similarly fucose presents the same for certain ...