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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. Antibodies can recognize virtually any size antigen with diverse chemical compositions from molecules. Each antibody recognizes one or more specific antigens. Antigen literally means "antibody generator", as it is the presence of an antigen that drives the formation of an antigen-specific antibody. Each tip of the "Y" of an antibody contains a paratope that specifically binds to one particular epitope on an antigen, allowing the two molecules to bind together with precision. Using this mechanism, antibodies can effectively "tag" a microbe or an infected cell for attack by other parts of the immune system, or can neutralize it directly.
In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage. They are found in both embryonic and adult organisms, but they have slightly different properties in each. They are usually distinguished from progenitor cells, which cannot divide indefinitely, and precursor or blast cells, which are usually committed to differentiating into one cell type.
Macrophages are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris, and foreign substances, which do not have proteins that are specific to healthy body cells on their surface. This process is called phagocytosis, which acts to defend the host against infection and injury.
T cells are one of the important types of white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell surface.
A cytotoxic T cell (also known as TC, cytotoxic T lymphocyte, CTL, T-killer cell, cytolytic T cell, CD8+ T-cell or killer T cell) is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected by intracellular pathogens (such as viruses or bacteria), or cells that are damaged in other ways.
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.
The plasma membranes of cells contain combinations of glycosphingolipids, cholesterol and protein receptors organised in glycolipoprotein lipid microdomains termed lipid rafts. Their existence in cellular membranes remains controversial. Indeed, Kervin and Overduin imply that lipid rafts are misconstrued protein islands, which they propose form through a proteolipid code. Nonetheless, it has been proposed that they are specialized membrane microdomains which compartmentalize cellular processes by serving as organising centers for the assembly of signaling molecules, allowing a closer interaction of protein receptors and their effectors to promote kinetically favorable interactions necessary for the signal transduction. Lipid rafts influence membrane fluidity and membrane protein trafficking, thereby regulating neurotransmission and receptor trafficking. Lipid rafts are more ordered and tightly packed than the surrounding bilayer, but float freely within the membrane bilayer. Although more common in the cell membrane, lipid rafts have also been reported in other parts of the cell, such as the Golgi apparatus and lysosomes.
Glycolipids are lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the connections that allow cells to connect to one another to form tissues. Glycolipids are found on the surface of all eukaryotic cell membranes, where they extend from the phospholipid bilayer into the extracellular environment.
Sphingolipids are a class of lipids containing a backbone of sphingoid bases, which are a set of aliphatic amino alcohols that includes sphingosine. They were discovered in brain extracts in the 1870s and were named after the mythological sphinx because of their enigmatic nature. These compounds play important roles in signal transduction and cell recognition. Sphingolipidoses, or disorders of sphingolipid metabolism, have particular impact on neural tissue. A sphingolipid with a terminal hydroxyl group is a ceramide. Other common groups bonded to the terminal oxygen atom include phosphocholine, yielding a sphingomyelin, and various sugar monomers or dimers, yielding cerebrosides and globosides, respectively. Cerebrosides and globosides are collectively known as glycosphingolipids.
CD1 is a family of glycoproteins expressed on the surface of various human antigen-presenting cells. CD1 glycoproteins are structurally related to the class I MHC molecules, however, in contrast to MHC class 1 proteins, they present lipids, glycolipids and small molecules antigens, from both endogenous and pathogenic proteins, to T cells and activate an immune response. Both αβ and γδ T cells recognise CD1 molecules.
In immunology, clonal selection theory explains the functions of cells of the immune system (lymphocytes) in response to specific antigens invading the body. The concept was introduced by Australian doctor Frank Macfarlane Burnet in 1957, in an attempt to explain the great diversity of antibodies formed during initiation of the immune response. The theory has become the widely accepted model for how the human immune system responds to infection and how certain types of B and T lymphocytes are selected for destruction of specific antigens.
Memory T cells are a subset of T lymphocytes that might have some of the same functions as memory B cells. Their lineage is unclear.
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.
Sialyl LewisX (sLeX), also known as cluster of differentiation 15s (CD15s) or stage-specific embryonic antigen 1 (SSEA-1), is a tetrasaccharide carbohydrate which is usually attached to O-glycans on the surface of cells. It is known to play a vital role in cell-to-cell recognition processes. It is also the means by which an egg attracts sperm; first, to stick to it, then bond with it and eventually form a zygote.
Globosides are a sub-class of the lipid class glycosphingolipid with three to nine sugar molecules as the side chain of ceramide. The sugars are usually a combination of N-acetylgalactosamine, D-glucose or D-galactose. One characteristic of globosides is that the "core" sugars consists of Glucose-Galactose-Galactose (Ceramide-βGlc4-1βGal4-1αGal), like in the case of the most basic globoside, globotriaosylceramide (Gb3), also known as pk-antigen. Another important characteristic of globosides is that they are neutral at pH 7, because they usually do not contain neuraminic acid, a sugar with an acidic carboxy-group. However, some globosides with the core structure Cer-Glc-Gal-Gal do contain neuraminic acid, e.g. the globo-series glycosphingolipid "SSEA-4-antigen".
Induced pluripotent stem cells are a type of pluripotent stem cell that can be generated directly from a somatic cell. The iPSC technology was pioneered by Shinya Yamanaka and Kazutoshi Takahashi in Kyoto, Japan, who together showed in 2006 that the introduction of four specific genes, collectively known as Yamanaka factors, encoding transcription factors could convert somatic cells into pluripotent stem cells. Shinya Yamanaka was awarded the 2012 Nobel Prize along with Sir John Gurdon "for the discovery that mature cells can be reprogrammed to become pluripotent."
SRY -box 2, also known as SOX2, is a transcription factor that is essential for maintaining self-renewal, or pluripotency, of undifferentiated embryonic stem cells. Sox2 has a critical role in maintenance of embryonic and neural stem cells.
Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) also known as CD66e, is a member of the carcinoembryonic antigen (CEA) gene family.
The NTERA-2 cell line is a clonally derived, pluripotent human embryonal carcinoma cell line.
Globo H (globohexaosylceramide) is a globo-series glycosphingolipid antigen that is present on the outer membrane of some cancer cells. Globo H is not expressed in normal tissue cells, but is expressed in a number of types of cancers, including cancers of the breast, prostate, and pancreas. Globo H's exclusivity for cancer cells makes it a target of interest for cancer therapies.
References
- ↑ Thudichum, John Louis William (1884). A Treatise on the Chemical Constitution of Brain. London: Bailliere, Tindall, and Cox. OCLC 253038666.
- ↑ Futerman, AH; Hannun, YA (2004). "The complex life of simple sphingolipids". EMBO Reports. 5 (8): 777–782. doi:10.1038/sj.embor.7400208. PMC 1299119 . PMID 15289826.
- ↑ Kuroda, Yasumasa; Kitada, Masaaki; Wakao, Shohei; Nishikawa, Kouki; Tanimura, Yukihiro; Makinoshima, Hideki; Goda, Makoto; Akashi, Hideo; Inutsuka, Ayumu (2010-05-11). "Unique multipotent cells in adult human mesenchymal cell populations". Proceedings of the National Academy of Sciences of the United States of America. 107 (19): 8639–8643. doi: 10.1073/pnas.0911647107 . ISSN 1091-6490. PMC 2889306 . PMID 20421459.
- ↑ Byrne, James (2022-02-16). "A mini-review on stage-specific embryonic antigen 3 (SSEA-3)". eJournal of Cellular Biotechnology (in Italian). 1:eP3.