Search results
Results from the WOW.Com Content Network
Histamine has two basic centres, namely the aliphatic amino group and whichever nitrogen atom of the imidazole ring does not already have a proton. Under physiological conditions, the aliphatic amino group (having a pK a around 9.4) will be protonated, whereas the second nitrogen of the imidazole ring (pK a ≈ 5.8) will not be protonated. [11]
In mammals, histamine is an important biogenic amine with regulatory roles in neurotransmission, gastric acid secretion and immune response. [1] [2] Histidine decarboxylase is the sole member of the histamine synthesis pathway, producing histamine in a one-step reaction. Histamine cannot be generated by any other known enzyme.
Histamine is a weak base (a compound able to react with a hydrogen ion to form an acid) that can link with acid groups within the granules of the mast cells. [8] The mechanism of the displacement theory. The crux of this theory lies in the assumption that histamine liberators release histamine by displacing it from cells.
The cells of the adaptive immune system are special types of leukocytes, called lymphocytes. B cells and T cells are the major types of lymphocytes and are derived from hematopoietic stem cells in the bone marrow. [57] B cells are involved in the humoral immune response, whereas T cells are involved in cell-mediated immune response.
A mast cell (also known as a mastocyte or a labrocyte [1]) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a part of the immune and neuroimmune systems.
H 4 receptor H4 Receptors: Initially discovered on immune cells, particularly mast cells, eosinophils, and T cells, H4 receptors are involved in immune responses, including chemotaxis (cellular movement in response to chemical signals) and cytokine production. These receptors play a role in inflammation and allergic reactions.
H 1-antihistamines work by binding to histamine H 1 receptors in mast cells, smooth muscle, and endothelium in the body as well as in the tuberomammillary nucleus in the brain. Antihistamines that target the histamine H 1-receptor are used to treat allergic reactions in the nose (e.g., itching, runny nose, and
Histamine is a ubiquitous messenger molecule released from mast cells, enterochromaffin-like cells, and neurons. [5] Its various actions are mediated by histamine receptors H 1 , H 2 , H 3 and H 4 . The histamine receptor H 2 belongs to the rhodopsin -like family of G protein-coupled receptors .