Definition of receptors
Receptors are proteins, usually, cell surface receptors, that bind ligands and elicit responses in the immune system, including cytokine receptors, growth factor receptors, and the Fc receptor. Receptors can be found on various immune cells such as B cells, T cells, NK cells, monocytes, and stem cells. A molecule that binds to a receptor is called a ligand and can be a peptide (short protein) or another small molecule, such as a neurotransmitter, hormone, drug, toxin, or foreign parts of a virus or microbe. When a ligand binds to its corresponding receptor, it activates or inhibits the receptor’s associated biochemical pathway. Receptors can induce cell growth, division, and death; control membrane channels or regulate cell attachment. The receptors play important roles in signal transduction, immunotherapy, and immune responses.
Growth factor receptors
Growth factors and their receptor recombinants play an important role in the regulation of cell division, development, and differentiation. Growth factor receptors include wnt receptor, tie, neurotrophin receptor, ephrin receptor, insulin-like growth factor receptor (IGF receptor), epidermal growth factor receptor (EGF receptor), epidermal growth factor receptor (EGF receptor), fibroblast growth factor (FGF receptor), platelet-derived growth factor receptor (PDGF receptor), and vascular endothelial growth factor receptor (VEGF receptor), etc.
The expression patterns of cytokine receptors are products of differentiation and allow changes in physiological regulation. These cytokine receptors allow cells to communicate with the extracellular environment by responding to signals generated in the vicinity or elsewhere in the body. Thus, the initial binding of cytokines to their receptors is a key event that occurs rapidly, at very low cytokine concentrations, is usually virtually irreversible, and leads to intracellular changes that result in a biological response. The biological response can vary between cytokine receptors and from cell to cell, but generally involves gene expression, cell cycle changes, and the release of mediators such as the cytokines themselves.
B cell receptor
B cells, also called B lymphocytes, developed in the bone marrow of most mammals, circulating in the blood and lymph. One of the main functions of a B cell is the production of antibodies, which aid in adaptive immunity, complement activation, and the induction of allergic responses.
T cell receptor
The T cell antigen receptor (TCR) is the main defining marker of all T cells. Also associated with the TCR is a complex of proteins known as CD3, which is involved in intracellular signal transduction after the TCR is cleaved. binds to its cognate MHC/antigen complex. With the help of the chemokine receptor CCR5 or CXCR4, HIV binds to CD4 and penetrates its nucleic acid into the host cell. This causes the destruction of CD4 T cells and the collapse of the immune system.
Granulocyte is a type of immune cell that has granules with enzymes released during infections, allergic reactions, and asthma. A granulocyte is a type of white blood cell. Neutrophils, eosinophils, and basophils are three different forms of granulocytes. Granulocytes are crucial players in innate and adaptive immunity expressing a large number of cell surface receptors for recognition of invading pathogens and the inflammatory environment. These include G protein-coupled chemokine receptors, Fc receptors, various cytokine receptors, as well as innate immune receptors such as toll-like receptors and C-type lectins.