The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are considered essential in B cell antibody class switching, breaking cross-tolerance in dendritic cells, in the activation and growth of cytotoxic T cells, and in maximizing bactericidal activity of phagocytes such as macrophages and neutrophils. CD4+ cells are mature Th cells that express the surface protein CD4. Genetic variation in regulatory elements expressed by CD4+ cells determines susceptibility to a broad class of autoimmune diseases.
CD32, also known as FcγRII or FCGR2, is a surface receptor glycoprotein belonging to the Ig gene superfamily. CD32 can be found on the surface of a variety of immune cells. CD32 has a low-affinity for the Fc region of IgG antibodies in monomeric form, but high affinity for IgG immune complexes. CD32 has two major functions: cellular response regulation, and the uptake of immune complexes. Cellular responses regulated by CD32 include phagocytosis, cytokine stimulation, and endocytic transport. Dysregulated CD32 is associated with different forms of autoimmunity, including systemic lupus erythematosus. In humans, there are three major CD32 subtypes: CD32A, CD32B, and CD32C. While CD32A and CD32C are involved in activating cellular responses, CD32B is inhibitory.
CD23, also known as Fc epsilon RII, or FcεRII, is the "low-affinity" receptor for IgE, an antibody isotype involved in allergy and resistance to parasites, and is important in regulation of IgE levels. Unlike many of the antibody receptors, CD23 is a C-type lectin. It is found on mature B cells, activated macrophages, eosinophils, follicular dendritic cells, and platelets.
L-selectin, also known as CD62L, is a cell adhesion molecule found on the cell surface of leukocytes, and the blastocyst. It is coded for in the human by the SELL gene. L-selectin belongs to the selectin family of proteins, which recognize sialylated carbohydrate groups containing a Sialyl LewisX (sLeX) determinant. L-selectin plays an important role in both the innate and adaptive immune responses by facilitating leukocyte-endothelial cell adhesion events. These tethering interactions are essential for the trafficking of monocytes and neutrophils into inflamed tissue as well as the homing of lymphocytes to secondary lymphoid organs. L-selectin is also expressed by lymphoid primed hematopoietic stem cells and may participate in the migration of these stem cells to the primary lymphoid organs. In addition to its function in the immune response, L-selectin is expressed on embryonic cells and facilitates the attachment of the blastocyst to the endometrial endothelium during human embryo implantation.
Follicular dendritic cells (FDC) are cells of the immune system found in primary and secondary lymph follicles of the B cell areas of the lymphoid tissue. Unlike dendritic cells (DC), FDCs are not derived from the bone-marrow hematopoietic stem cell, but are of mesenchymal origin. Possible functions of FDC include: organizing lymphoid tissue's cells and microarchitecture, capturing antigen to support B cell, promoting debris removal from germinal centers, and protecting against autoimmunity. Disease processes that FDC may contribute include primary FDC-tumor, chronic inflammatory conditions, HIV-1 infection development, and neuroinvasive scrapie.
Mucosal vascular addressin cell adhesion molecule 1 (MAdCAM-1) is a protein that in humans is encoded by the MADCAM1 gene. The protein encoded by this gene is an endothelial cell adhesion molecule that interacts preferentially with the leukocyte beta7 integrin LPAM-1, L-selectin, and VLA-4 on myeloid cells to direct leukocytes into mucosal and inflamed tissues. It is a member of the immunoglobulin superfamily and is similar to ICAM-1 and VCAM-1.
Chemokine ligand 21 (CCL21) is a small cytokine belonging to the CC chemokine family. This chemokine is also known as 6Ckine, exodus-2, and secondary lymphoid-tissue chemokine (SLC). CCL21 elicits its effects by binding to a cell surface chemokine receptor known as CCR7. The main function of CCL21 is to guide CCR7 expressing leukocytes to the secondary lymphoid organs, such as lymph nodes and Peyer´s patches.
CD22, or cluster of differentiation-22, is a molecule belonging to the SIGLEC family of lectins. It is found on the surface of mature B cells and to a lesser extent on some immature B cells. Generally speaking, CD22 is a regulatory molecule that prevents the overactivation of the immune system and the development of autoimmune diseases.
CD137, a member of the tumor necrosis factor (TNF) receptor family, is a type 1 transmembrane protein, expressed on surfaces of leukocytes and non-immune cells. Its alternative names are tumor necrosis factor receptor superfamily member 9 (TNFRSF9), 4-1BB, and induced by lymphocyte activation (ILA). It is of interest to immunologists as a co-stimulatory immune checkpoint molecule, and as a potential target in cancer immunotherapy.
C-C chemokine receptor type 7 is a protein that in humans is encoded by the CCR7 gene. Two ligands have been identified for this receptor: the chemokines ligand 19 (CCL19/ELC) and ligand 21 (CCL21). The ligands have similar affinity for the receptor, though CCL19 has been shown to induce internalisation of CCR7 and desensitisation of the cell to CCL19/CCL21 signals. CCR7 is a transmembrane protein with 7 transmembrane domains, which is coupled with heterotrimeric G proteins, which transduce the signal downstream through various signalling cascades. The main function of the receptor is to guide immune cells to immune organs by detecting specific chemokines, which these tissues secrete.
Intercellular adhesion molecule 3 (ICAM3) also known as CD50, is a protein that in humans is encoded by the ICAM3 gene. The protein is constitutively expressed on the surface of leukocytes, which are also called white blood cells and are part of the immune system. ICAM3 mediates adhesion between cells by binding to specific integrin receptors. It plays an important role in the immune cell response through its facilitation of interactions between T cells and dendritic cells, which allows for T cell activation. ICAM3 also mediates the clearance of cells undergoing apoptosis by attracting and binding macrophages, a type of cell that breaks down infected or dying cells through a process known as phagocytosis, to apoptotic cells.
Junctional adhesion molecule A is a protein that in humans is encoded by the F11R gene. It has also been designated as CD321.
CD226, PTA1 or DNAM-1 is a ~65 kDa immunoglobulin-like transmembrane glycoprotein expressed on the surface of natural killer cells, NK T cell, B cells, dendritic cells, hematopoietic precursor cells, platelets, monocytes and T cells.
Lymphocyte-activation gene 3, also known as LAG-3, is a protein which in humans is encoded by the LAG3 gene. LAG3, which was discovered in 1990 and was designated CD223 after the Seventh Human Leucocyte Differentiation Antigen Workshop in 2000, is a cell surface molecule with diverse biologic effects on T cell function. It is an immune checkpoint receptor and as such is the target of various drug development programs by pharmaceutical companies seeking to develop new treatments for cancer and autoimmune disorders. In soluble form it is also being developed as a cancer drug in its own right.
The following outline is provided as an overview of and topical guide to immunology:
Eugene C. "Gene" Butcher is an American immunologist and a professor of pathology at Stanford University School of Medicine.
Gut-specific homing is the mechanism by which activated T cells and antibody-secreting cells (ASCs) are targeted to both inflamed and non-inflamed regions of the gut in order to provide an effective immune response. This process relies on the key interaction between the integrin α4β7 and the addressin MadCAM-1 on the surfaces of the appropriate cells. Additionally, this interaction is strengthened by the presence of CCR9, a chemokine receptor, which interacts with TECK. Vitamin A-derived retinoic acid regulates the expression of these cell surface proteins.
The Vergara family is one of the most aristocratic families of Colombia and Chile with origins in Bergara, Spain. Had its period of greatest influence between the 17th, 18th, and 19th centuries. The family is spread across several branches in Spain, Colombia, Chile and the US. Considered one of the first families of Spaniards in the Americas having arrived first as conquistadors, and royal officers of the Spanish crown. The Vergara Family have produced four presidents of Colombia by the same surname; and three more related by blood. Other branch is considered amongst the founding families of Chile. Originally from Gipuzkoa, Spain, more specifically from Bergara, the Municipality in Basque Country.
Integrin α4β7 is an integrin heterodimer composed of CD49d (alpha-4) subunit and beta-7 subunit noncovalently linked. LPAM-1 is expressed on the cell surface of leukocytes. This receptor is involved in lymphocyte trafficking pathway to site of inflammation in intestinal tissues.
