tissue typing


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Tissue Typing

 

Definition

Tissue typing is a group of procedures that determines the type of histocompatibility antigens on a person's cells or tissues. This procedure is typically used prior to transplantation of tissues or organs.

Purpose

Tissue typing is done prior to transplantation to ensure as close a match as possible between the donor and the recipient. If the histocompatibility antigens do not match well, there is a much greater chance that the recipient will reject the donated tissue.
Histocompatibility antigens are molecules on the surface of all cells in the body. The specific types of histocompatibility antigens present on a person's cells determine their identity and distinguish each person. They are a "fingerprint."
Each person has a unique set of histocompatibility antigens. If the antigens on tissue or organs from a donor do not match that of the recipient, a rejection response can occur. The recipient's immune system will detect the difference between the two sets of antigen and start a rejection response to kill the donated tissue. Except in the case of identical twins, no two people are identical in terms of their histocompatibility antigen types. However, the closer two tissues come to matching, the more likely the recipient will accept the donated tissue or organ.
Human Lymphocyte Antigens (HLA) is the name given to the most commonly used histocompatibility antigens. The antigens can be grouped into two classes: class I antigens are found on almost all cells, and class II antigens are normally found only on B lymphocytes, macrophages, monocytes, dendritic cells, and endothelial cells.

Description

Generally, typing is performed on blood cells because they are an easy sample to obtain. Blood is withdrawn from a vein in the forearm, and the cells are separated. There are a number of different techniques used to identify the antigens on the cells. Typically, specific antibodies react with the cells. Each antibody preparation is specific for one histocompatibility antigen. If the antigen is present, the antibody will bind to it. Laboratory instruments are used to detect antibody binding to the cells. Class II antigens are determined by the mixed lymphocyte reaction (MLR) or by a polymerase chain reaction (PCR). In the mixed lymphocyte reaction, lymphocyte replication occurs if there is a mismatch, and is detected by a specific assay. The PCR test is a new DNA-based test that can detect the presence or absence of antigens by determining whether cells have the genes for the antigens.
One type of transplant does not require tissue typing. In the case of corneal transplants, tissue typing is not needed because cornea do not have their own blood supply. This greatly reduces the chance that immune cells will come in contact with the cornea and recognize it as foreign. For this reason, corneas can be transplant from any person, and there is little chance of rejection.

Normal results

Because each person has their own histocompatibility antigen "fingerprint," there is no true normal result. Each fingerprint is unique.

Resources

Books

Berkow, Robert, editor. Merck Manual of Medical Information. Whitehouse Station, NJ: Merck Research Laboratories, 1997.

Key terms

Antibody — A molecule produced by the body that is part of the immune response to attack antigens.
Antigen — A molecule that causes the body to produce an immunological response to attack the antigen.
Cornea — The transparent outer layer of the eye. It covers the iris and lens.
Lymphocyte — A class of white blood cells that are responsible for creating the immune response to antigens.

tissue

 [tish´u]
a group or layer of similarly specialized cells that together perform certain special functions.
adenoid tissue lymphoid tissue.
adipose tissue connective tissue made of fat cells in a meshwork of areolar tissue.
areolar tissue connective tissue made up largely of interlacing fibers.
bony tissue osseous tissue.
brown adipose tissue (brown fat tissue) brown fat.
bursa-equivalent tissue (bursal equivalent tissue) a hypothesized lymphoid tissue in nonavian vertebrates including human beings, equivalent to the bursa of Fabricius in birds: the site of B lymphocyte maturation. It now appears that B lymphocyte maturation occurs primarily in the bone marrow.
cancellous tissue the spongy tissue of bone.
cartilaginous tissue the substance of cartilage.
chordal tissue the tissue of the notochord.
chromaffin tissue a tissue composed largely of chromaffin cells, well supplied with nerves and vessels; it occurs in the adrenal medulla and also forms the paraganglia of the body.
cicatricial tissue the dense fibrous tissue forming a cicatrix, derived directly from granulation tissue; called also scar tissue.
connective tissue the tissue that binds together and is the support of the various structures of the body; see also connective tissue.
elastic tissue connective tissue made up of yellow elastic fibers, frequently massed into sheets.
endothelial tissue peculiar connective tissue lining serous and lymph spaces.
epithelial tissue a general name for tissues not derived from the mesoderm.
erectile tissue spongy tissue that expands and becomes hard when filled with blood.
fatty tissue connective tissue made of fat cells in a meshwork of areolar tissue.
fibrous tissue the common connective tissue of the body, composed of yellow or white parallel elastic and collagen fibers.
gelatinous tissue mucous tissue.
granulation tissue material formed in repair of wounds of soft tissue, consisting of connective tissue cells and ingrowing young vessels; it ultimately forms cicatrix.
gut-associated lymphoid tissue (GALT) lymphoid tissue associated with the gut, including the tonsils, Peyer's patches, lamina propria of the gastrointestinal tract, and appendix.
indifferent tissue undifferentiated embryonic tissue.
interstitial tissue connective tissue between the cellular elements of a structure.
lymphadenoid tissue tissue resembling that of lymph nodes, spleen, bone marrow, tonsils, and lymph vessels.
lymphoid tissue a latticework of reticular tissue whose interspaces contain lymphocytes.
mesenchymal tissue embryonic connective tissue composed of stellate cells and a ground substance of coagulable fluid.
mucous tissue a jellylike connective tissue, such as occurs in the umbilical cord. Called also gelatinous tissue.
muscular tissue the substance of muscle.
myeloid tissue red bone marrow.
nerve tissue (nervous tissue) the specialized tissue forming the elements of the nervous system.
osseous tissue the specialized tissue forming the bones.
reticular tissue (reticulated tissue) connective tissue composed predominantly of reticulum cells and reticular fibers.
scar tissue cicatricial tissue.
sclerous t's the cartilaginous, fibrous, and osseous tissues.
skeletal tissue the bony, ligamentous, fibrous, and cartilaginous tissue forming the skeleton and its attachments.
splenic tissue red pulp.
subcutaneous tissue the layer of loose connective tissue directly under the skin.
tissue typing identification of tissue types for purposes of predicting acceptance or rejection of grafts and transplants. The process and purposes of tissue typing are essentially the same as for blood typing. The major difference lies in the kinds of antigens being evaluated. The acceptance of allografts depends on the hla antigens (HLA); if the donor and recipient are not HLA identical, the allograft is rejected, sometimes within minutes. The HLA genes are located in the major histocompatibility complex, a region on the short arm of chromosome 6, and are involved in cell-cell interaction, immune response, organ transplantation, development of cancer, and susceptibility to disease. There are five genetic loci, designated HLA-A, HLA-B, HLA-C, HLA-D, and HLA-DR. At each locus, there can be any of several different alleles.



Each person inherits one chromosome 6 from the mother and one from the father; that is, each parent transmits to the child one allele for each kind of antigen (A, B, C, D, and DR). If the parents are different at both alleles of a locus, the statistical chance of one sibling being identical to another is one in four (25 per cent), the chance of being identical at one allele only (half-identical) is 50 per cent, and the chance of a total mismatch is 25 per cent.
Techniques for Tissue Typing. Histocompatibility testing involves several basic methods of assay for HLA differences. The most widely used method uses the polymerase chain reaction to compare the DNA of the person, organ, or graft being tested with known pieces of the genes encoding MHC antigens. The variability of these regions of the genes determines the tissue type of the subject.



Serologic methods are used to detect serologically defined antigens on the surfaces of cells. In general, HLA-A, -B, and -C determinants are primarily measured by serologic techniques. A second method, involving lymphocyte reactivity in a mixed lymphocyte culture, for determining HLA-D or lymphocyte-defined antigens, is now only rarely used.

Essentially, the serologic method is performed by incubating target lymphocytes (isolated from fresh peripheral blood) with antisera that recognize all known HLA antigens. The cells are spread in a tray with microscopic wells containing various kinds of antisera and are incubated for 30 minutes, followed by an additional 60-minute complement incubation. If the lymphocytes have on their surfaces antigens recognized by the antibodies in the antiserum, the lymphocytes are lysed. A dye is added to show changes in the permeability of the cell membrane and cellular death. The proportion of cells destroyed by lysis indicates the degree of histologic incompatibility. If, for example, the lymphocytes from a person being tested for HLA-A3 are destroyed in a well containing antisera for HLA-A3, the test is positive for this antigen group.
white adipose tissue (yellow adipose tissue) the adipose tissue composing the bulk of the body fat.

typing

 [tīp´ing]
in transplantation immunology, a method of measuring the degree of organ, solid tissue, or blood compatibility between two individuals, in which specific histocompatibility antigens (such as those on leukocytes or erythrocytes) are detected by means of suitable isoimmune antisera.
blood typing (typing of blood) determining the character of the blood on the basis of agglutinogens in the erythrocytes; see also blood group.
phage typing characterization of bacteria, extending to strain differences, by demonstration of susceptibility to one or more races (a spectrum) of bacteriophage; widely applied to staphylococci, typhoid bacilli, and other organisms for epidemiological purposes.
tissue typing identification of the human leukocyte antigens of the donor and recipient of a transplant or transfusion; see also tissue typing.

tissue typing

The identification of particular chemical groups present on the surface of all body cells and specific to the individual. These groups are called the histocompatibility antigens and include the human leukocyte antigens (HLAs) which are short chains of linked amino acids unique to each person except that they are shared by identical twins. Tissue typing is important in organ donation to reduce the risk of rejection. See also MAJOR HISTOCOMPATIBILITY COMPLEX.
References in periodicals archive ?
Michael Cecka, MD, a UCLA professor of pathology and laboratory medicine, observed: "Not only has tissue typing been key to the success of bone marrow transplants and prolonged graft survival for patients fortunate to receive a well-matched kidney transplant, but the cross-match test he developed in the 1960s is still used today for all kidney transplant patients and select candidates for heart, lungs, pancreata, bowels and sometimes liver transplantation to avoid catastrophic rejections that are mediated by antibodies against the donor's human leukocyte antigens."
The July ruling makes PGD licensable in cases where tissue typing is the sole purpose of testing.
"These reviews will include the policy areas surrounding sperm, egg and embryo donation, pre-implantation tissue typing and the welfare of the child assessment."
(1) Others consider there to be an absolute difference between pre-implantation diagnosis for a serious disease, which they find acceptable, and tissue typing to create an embryo for treating an existing child, irrespective of any risks to that embryo.
He first used standard tissue typing methods to study blood samples from a series of 61 Norwegian MS patients, and found that 59 of them were positive for DR2, 4 or 6.
Then we would enter the tissue type into a computer and store it." At a cost of about $350 for each tissue typing, even a relatively small donor file could easily cost $1 million.
The micro lymphocytotoxicity test ultimately became the international standard for tissue typing.
HBOS Foundation has donated pounds 5,000 to cover the cost of tissue typing 70 people from the ECHO clinic.
Mr Justice Maurice Kay ruled that the HFEA had overstepped its powers in licensing embryo selection by tissue typing and had not correctly understood the 1990 Human Fertilisation and Embryology Act.
HBOS Foundation have donated pounds 5,000 to cover the cost of tissue typing 70 people from the ECHO clinic.
It said such a 'tissue typing' procedure would be unlawful and unethical as it would break the law on human fertilisation and embryology.

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