AntigenIn immunology, an antigen (Ag) is a molecule, or portion thereof, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. Antigens can be proteins, peptides (amino acid chains), polysaccharides (chains of simple sugars), lipids, or nucleic acids. Antigens exist on normal cells, cancer cells, parasites, viruses, fungi, and bacteria.
Staphylococcus aureusStaphylococcus aureus is a gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive for catalase and nitrate reduction and is a facultative anaerobe, meaning that it can grow without oxygen.
PolysaccharidePolysaccharides (; from Ancient Greek (polús)'many, much' and (sákkhar)'sugar') are "compounds consisting of a large number of monosaccharides linked glycosidically". They are the most abundant carbohydrates in food. Their structures range from linear to highly branched polymers. Examples include storage polysaccharides such as starch, glycogen, and galactogen and structural polysaccharides such as hemicellulose and chitin.
ProteinBiomolecule consisting of chains of amino acid residuesA representation of the 3D structure of the protein myoglobin showing turquoise α-helices. This protein was the first to have its structure solved by X-ray crystallography. Toward the right-center among the coils, a prosthetic group called a heme group (shown in gray) with a bound oxygen molecule (red).Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acidresidues.
AntibodyAn antibody (Ab), or immunoglobulin (Ig), is a large protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as those that exist on bacteria and virus cells, including those that cause disease. Each individual antibody recognizes one or more specific antigens, and antigens (a portmanteau of "antibody generator") of virtually any size and chemical composition can be recognized.
Cell wallA cell wall is a structural layer that surrounds some cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, and functions as a selective barrier. Another vital role of the cell wall is to help the cell withstand osmotic pressure and mechanical stress. Cell walls are found in most prokaryotes, with the exception of mollicute bacteria.
Two-component regulatory systemIn molecular biology, a two-component regulatory system serves as a basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions. Two-component systems typically consist of a membrane-bound histidine kinase that senses a specific environmental stimulus, and a corresponding response regulator that mediates the cellular response, mostly through differential expression of target genes.
Fragment antigen-binding regionThe fragment antigen-binding region (Fab region) is a region on an antibody that binds to antigens. It is composed of one constant and one variable domain of each of the heavy and the light chain. The variable domain contains the paratope (the antigen-binding site), comprising a set of complementarity-determining regions, at the amino terminal end of the monomer. Each arm of the Y thus binds an epitope on the antigen.
PhagocytosisPhagocytosis (from Ancient Greekφαγεῖν (phagein)'to eat' and κύτος (kytos)'cell') is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is called a phagocyte. In a multicellular organism'simmune system, phagocytosis is a major mechanism used to remove pathogens and cell debris.
Fragment crystallizable regionThe fragment crystallizable region (Fc region) is the tail region of an antibody that interacts with cell surface receptors called Fc receptors and some proteins of the complement system. This region allows antibodies to activate the immune system, for example, through binding to Fc receptors.
OpsoninOpsonins are that, when bound to substances or cells, induce phagocytes to phagocytose the substances or cells with the opsonins bound. Thus, opsonins act as tags to label things in the body that should be phagocytosed (i.e. eaten) by phagocytes (cells that specialise in phagocytosis, i.e. cellular eating).
Immunoglobulin GImmunoglobulin G (IgG) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG antibody has two paratopes. FunctionAntibodies are major components of humoral immunity. IgG is the main type of antibody found in blood and extracellular fluid, allowing it to control infection of body tissues.*As an Amazon Associate I earn from qualifying purchases.