Posts Tagged ‘Histocompatibility’
CD4/CD8, the identification unit depends blood lymphocytes specific cell surface antigens, which can be detected with monoclonal antibodies using flow cytometry. Increased in: Rheumatoid arthritis, type I diabetes, SLE without kidney disease, primary biliary cirrhosis, atopic dermatitis, Sezary syndrome, psoriasis, autoimmune chronic hepatitis. Gradual decline in the number and function of CD4 appears to be the most characteristic immunological defects in AIDS. Absolute measurement of CD4 is particularly useful for determining the eligibility of therapy and monitoring of disease progression. CD4 cells are primarily cells of the immune system helperinducer. They react with peptide antigens to class II major histocompatibility complex and to increase B-cell responses and T cell lymphokine secretion. CD4 cells are decreased in: AIDS / HIV, systemic lupus erythematosus with renal impairment, acute CMV infection, burns, graft against the host, sunburn, myelodysplastic syndromes, acute lymphocytic leukemia in remission, recovery of bone marrow transplant, herpes infection, infectious mononucleosis, measles, ataxiatelangiectasia, vigorous exercise. cells / ul
HLA typing can provide a valuable basis of DNA evidence helping to determine the identity in criminal cases. This technology has been used in national trials for criminal cases. Furthermore, it is a technology that has been applied internationally in the field of human rights. For example, HLA typing was a demand in Argentina following a military dictatorship that ended in 1983. The period of the dictatorship was marked by the murder and disappearance of thousands who were known or suspected of opposing the regime's practices. Missing children were often adopted by military and other officials. HLA typing was a tool used to determine parentage of children and non-return of the missing to their biological families. HLA typing has proven to be a valuable tool in studying the evolutionary origins of human populations. This information, in turn, contributes to a better understanding of cultural and linguistic practices between and within various ethnic groups. See also Antibody and antigen; Immunity, cell-mediated, immunity, humoral regulation; immunodeficiency syndromes, immunodeficiency diseases; Immunogenetics; immunological analysis techniques, genetics and immunology of transplantation
There is considerable variability in the frequency of HLA alleles between ethnic groups. This is reflected in anthropological studies that attempt to use HLA-types to determine migration patterns and the evolutionary relationships of populations of different ethnic origin. Ethnic variation is also reflected in studies of HLA-associated diseases. Generally, people who have been important reasons for migration and assimilation with other populations tend to have a pool of more diverse HLA genes. For example, it is unlikely that two unrelated individuals of African descent would have matched HLA types. Conversely, people who were isolated because of geography, cultural practices, and other historical influences may show a less diverse pool of HLA types, making it more likely for two unrelated individuals with HLA-compatible . There is a role for the HLA typing of individuals in various contexts. In most cases, HLA typing is used to determine whether an organ or tissue donor matches the recipient is appropriate for the types HLA-key to avoid creating a backlash in which the recipient's immune system attacks the tissue of the donor. In the particular case of bone marrow transplant, the risk for graft-versus-host disease, as opposed to tissue rejection. Because bone marrow contains cells of the immune system, the recipient actually receives the donor's immune system. If the immune system recognizes the donor tissues of the recipient as foreign, it can start to attack, causing inflammation and other complications of GVHD. As advances occur in transplant medicine, HLA typing for transplantation occurs with increasing frequency and in different contexts. There is a relationship between the inheritance of certain HLA types and susceptibility to specific diseases. Most often, these are diseases that are thought to be autoimmune in nature. Autoimmune diseases are those characterized by inflammatory reactions that occur as a result of the immune system mistakenly attacks self tissues. The basis of HLA association is not well understood, although there are some assumptions. Most autoimmune diseases are characterized by expression of MHC class II on cells of the body that are not normally express these proteins. This can confuse the killer T cells, which respond inappropriately attacking cells. Molecular mimicry is another hypothesis. Certain types of HLA antigens might look like from foreign organizations. If an individual is infected with a virus or bacterium foreign, the immune system mounts a response against the invader. However, there may be cross-reactive cells with the HLA type is taken to foreign antigen. Whatever the underlying mechanism, HLA-types are known factors that increase the relative risk of developing certain autoimmune diseases. For example, individuals who carry the HLA B-27 allele have a relative risk of 150 for the development of ankylosing spondylitis-direction of such a person has a chance to develop 150 times this form of arthritis column spine and pelvis, compared to someone in the general population of the population. Associations selected are listed below.
Major histocompatibility complex WORLD OF MICROBIOLOGY AND IMMUNOLOGY – The Major Histocompatibility Complex
ment recognized and targeted by phagocytes and complement proteins. Some stimulated B cells go on to become memory cells, which are able to mount an even faster response if the antigen is encountered again. Another type of acquired immunity involves killer Tcells and is called cellular immunity. T-cells through a process of maturation of the body called the thymus, wherein the T cells that recognize self antigens are eliminated. Each remaining T cells has the ability to recognize a single, specific, non-self-antigen that the body can meet. Although the names are similar, killer T cells are, unlike non-specific natural killer cells in that they are specific in their action. Some viruses and parasites quickly invade the body cells, where they are hidden from antibodies. Small pieces of proteins from these viruses or parasites that invade are presented on the surface of infected cells in conjunction with proteins of class I MHC, which are present on the surface most of all body cells. Killer T-cells can recognize antigen bound to MHC class I in this way, and they are encouraged to release chemicals that act directly to kill the infected cell. There is also a role for helper T cells and antigen-presenting cells in cellular immunity. Cytokine release Helper T cells, as in the humoral response, and cytokines stimulate the killer T cells to proliferate. Antigen-presenting cells carry foreign antigen in areas of the body where extra killer T cells can be alerted and recruited. The major histocompatibility complex clearly performs an important role in the immune system. Related to this role in immunity to disease, MHC is also important organ and tissue transplantation, as well as playing a role in susceptibility to certain diseases. HLA typing may also provide important information in parentage, legal, and anthropological studies.
MHC class III genes include the complement system. Complement proteins help activate and maintain the inflammatory process of an immune response. When a foreign organism enters the body, he is met by the components of natural immunity of the body. Innate immunity is the nonspecific first line of defense taken by the phagocytes, natural killer cells and components of the complement system. Phagocytes are specialized white blood cells that are able to engulf and kill an organism. Natural killer cells are specialized white blood cells that respond to certain cancer cells and viral infections. The complement system is a group of proteins called class III MHC antigens that attack. Antigens include any molecule capable of triggering an immune response. Although this list is not exhaustive, the antigens can be derived from toxins, proteins, carbohydrates, DNA or other molecules of viruses, bacteria, parasites, cell or cancer cells. The natural immune response will be a distant infection such as next line of defense mobilized through the acquisition, or specific, immunity. This specialized type of immunity is generally what is necessary to eliminate infection and is dependent on the role of proteins of major histocompatibility complex. There are two types of acquired immunity. Humoral immunity is important in the fight against infection outside the body cells, such as those caused by bacteria and some viruses. Other types of viruses and parasites that invade the cells are best tackled by cellular immunity. The main actors of acquired immunity are antigen-presenting cells, the Bcells, their secreted antibodies, and T-cells. Their functions are described in detail below. In humoral immunity, antigen-presenting cells, including some B-cells, engulf and break down foreign bodies. Antigens of these organisms are then brought to the outer surface of antigen presenting cells and presented in association with proteins of the MHC class II. The help of T cells recognize antigen presented in this way and release cytokines, proteins that signals B cells to take additional measures. Bcells are specialized white blood cells that mature in the bone marrow. Through the process of maturation, each B cell develops the ability to recognize and respond to a specific antigen. Helper T cells help to stimulate some B cells that can recognize a foreign antigen specific. B-cells that are stimulated in this manner develop into plasma cells, which secrete antibodies specific for the antigen recognized. Antibodies are proteins which are present in the circulation, as well as being bound to the surface of B cells They can destroy the foreign organism from which the antigen has come. Destruction occurs either directly or by marking the body, which will then be more easily rec • •
adjuvants. 1949 Macfarlane Burnet and Frank Fenner hypothesize immunological tolerance. 1959 Niels Jerne, David Talmage, Macfarlane Burnet develop the theory of clonal selection. 1957 Alick Isaacs and Jean Lindemann discover interferon. 1962 Rodney Porter and the team discover the structure of antibodies. 1962 James Miller and his team discover the involvement of the thymus in cellular immunity. Christmas 1962 Warner and his team distinguish between cellular and humoral immune responses. 1968 Anthony Davis and the team discover T cells and B cell cooperation in immune response. 1974 Peter Doherty and Rolf Zinkernagel explore major MHC restriction. 1985 Susumu Tonegawa, Leroy Hood, and the team to identify the immunoglobulin genes. 1987 Leroy Hood and his team to identify genes of T cell receptor 1985 Scientists are beginning to rapidly identify genes of immune cell that continues to this day. See also Antibody and antigen, B cells or B cells, the germ theory of disease, history of the development of antibiotics, history of public health, immunity, active, passive and delayed; immunity, mediated cellular, immunity, humoral regulation; infectious diseases and resistance; T cells or T cells
Histocompatibility refers to the means by which a eukaryotic cell can be identified. The phenomenon is the result of the presence of proteins on the surface of cells. These proteins are called histocompatibility molecules. Histocompatibility molecules on cells of an individual of a species are unique. Thus, if the cell is transplanted into another person, the cell will be recognized by the immune system as foreign. Histocompatibility molecules act as an antigen in the recipient, and therefore can also be called an antigen or histocompatibility transplantation antigen. This is the basis for the rejection of transplanted material. Identical twins have the same histocompatibility molecules on their cells. Thus, the tissue can be successfully transplanted from one individual to another, because the fabric will not be essentially foreign. However, for unrelated individuals, the cells have their own chemical signatures against histocompatibility molecules. Tissues of an individual will be recognized as foreign in another individual. All histocompatibility molecules present on the surface of a cell is also referred to as the histocompatibility complex. There are two classes of these molecules. The first class is called class I molecules These molecules are constituted by a part that is embedded in the cell membrane and a portion which protrudes from the outer surface of the membrane. The projecting part consists of protein and sugar. Certain human leukocyte antigens are examples of class I molecules The class I molecules function to chemically mark a cell so that the cell will be recognized and classified by T cells of the immune system. The T cell will recognize a region of major histocompatibility complex of "self." Because of this recognition, there will be no immune response initiated against the cell. But in another host, where the same region is chemically different from the Class I groups on host cells, the transplanted cells would be recognized as foreign by T cells
When T cells leave the thymus, they have unique antigen receptors as B cells do. Unlike B cells, T cells are unable to recognize an antigen present in the lymph, blood or tissue without help. The antigen must be presented to them by antigen-presenting cell. When an APC presents an antigen to viral or cancer cell, the antigen is first bound to major histocompatibility complex protein in the plasma membrane. The human MHC proteins are called HLA antigens. Because they mark the cell as belonging to a particular individual, the HLA antigens are self proteins. The importance of proteins in plasma membranes self was first recognized when he discovered that they contribute to tissue specificity and it is difficult to transplant tissue from one human to another. In other words, when the donor and recipient are compatible historical, a transplant is more likely to succeed. Figure 13.7 clonal selection theory, as applied to cytotoxic T cells. Figure 13.7 represents an antigen-presenting macrophages, represented by a red circle with a T cell specific. This T cell type of antigen receptor that combine with the specific antigen. In the figure, the different types of antigen receptors are represented by color. Antigen presentation leads to the activation of the T cell An activated T cell produces cytokines and undergoes clonal expansion. Cytokines are chemicals that stimulate different immune cell signaling to perform their functions. Many copies of the activated T cells are produced during clonal expansion. They destroy a cell, such as a cell infected with a virus or a cancer cell that displays antigen presented before. As the disease disappears, the immune response weakens, and less of cytokines are produced. Now, the activated T cells become sensitive to apoptosis. As mentioned previously, apoptosis is programmed cell death that contributes to homeostasis by regulating the number of cells in an organ, or in this one. Each T cell antigen receptor has different. cytokines antigen receptor
Lhermitte phenomenon Tingling or electric-like sensation felt as a result of neck flexion, said because of mechanosensitivity demyelinated axons. A major histocompatibility complex region on chromosome 6 which encodes immune response genes; possible area of genetic susceptibility in multiple sclerosis. Disease of the spinal cord myelopathy, usually weak and / or sensory disturbances below the level of demyelination. The plaque lesions of multiple sclerosis characterized pathologically by the gray light pink color in the regions of white matter central nervous system. relapse of neurological signs or symptoms occur in people with multiple sclerosis, persist for days to weeks, followed by a partial or complete recovery. Multiple sclerosis is an inflammatory, demyelinating disease of central nervous system causing
Presentation of the antigen presentation of antigens processed on the surface of macrophages, microglia and dendritic cells with concomitant major histocompatibility complex class II molecules is a necessary step for the generation and activation of antigen-specific T cells . Microglia are a major component of glial cells of the central nervous system of presumed origin of the bone marrow. Only perivascular microglia, a subtype, are regularly replaced from the bone marrow in adult animals, while parenchymal microglia are extremely sessile. Microglia respond to virtually any, even minor pathological events in the central nervous system. This article reviews the basic properties of microglia and discusses their multiple functions in the CNS during neurodegeneration, ischemia, autoimmunity and inflammation. I. BASICPROPERTIESOFMICROGLIA A. Microglia in normal CNS The CNS is composed of neurons and a soluble factor cytokine regulation of non-neuronal interactions between immune cells. Population of glial cells, designated, including microglia Nonneuronalcellsofthecentralnervoussystemencompassing glia, astrocytes and oligodendrocytes. major histocompatibility complex immunological surface molecules important in antigen-recognition process by T cells and self / nonself discrimination. A subpopulation of microglial cells in the glia central nervous system. biological membrane myelin around nerve fibers that facilitate rapid nerve conduction, produced by Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system. Regrowth of nerve regeneration after nerve injury. Synaptic detachment stripping active synapses of neurons by glial processes. Term Wallerian degeneration for the complex cellular and molecular events in the distal stump after nerve injury to a nerve fiber degeneration.