Tissue typing
Encyclopedia
Tissue typing is a procedure in which the tissues of a prospective donor and recipient are tested for compatibility prior to transplantation
. An embryo can be tissue typed to ensure that the embryo implanted can be a cord-blood stem cell donor for a sick sibling.
One technique of tissue typing, "mixed leukocyte reaction", is performed by culturing lymphocytes from the donor together with those from the recipient.
Another technique, known as a micro-cytotoxicity assay, utilizes serum with known anti-HLA antibodies that recognize particular HLA
loci (HLA-A, HLA-B, HLA-C, HLA-DP, HLA-DQ, HLA-DR) in order to match genetically similar individuals in hopes of performing a tissue transplantation. In this technique a donor's blood cells are MHC
typed by mixing them with serum
containing the anti-HLA antibodies. If the antibodies recognize their epitope
on the MHC then complement
activation occurs and the cell will be osmotically lysed
. Lysis results in the cell taking up a dye (trypan blue
). This allows identification of cell's MHC indirectly based on the specificity of the known antibodies in the serum.
Organ transplant
Organ transplantation is the moving of an organ from one body to another or from a donor site on the patient's own body, for the purpose of replacing the recipient's damaged or absent organ. The emerging field of regenerative medicine is allowing scientists and engineers to create organs to be...
. An embryo can be tissue typed to ensure that the embryo implanted can be a cord-blood stem cell donor for a sick sibling.
One technique of tissue typing, "mixed leukocyte reaction", is performed by culturing lymphocytes from the donor together with those from the recipient.
Another technique, known as a micro-cytotoxicity assay, utilizes serum with known anti-HLA antibodies that recognize particular HLA
Human leukocyte antigen
The human leukocyte antigen system is the name of the major histocompatibility complex in humans. The super locus contains a large number of genes related to immune system function in humans. This group of genes resides on chromosome 6, and encodes cell-surface antigen-presenting proteins and...
loci (HLA-A, HLA-B, HLA-C, HLA-DP, HLA-DQ, HLA-DR) in order to match genetically similar individuals in hopes of performing a tissue transplantation. In this technique a donor's blood cells are MHC
Major histocompatibility complex
Major histocompatibility complex is a cell surface molecule encoded by a large gene family in all vertebrates. MHC molecules mediate interactions of leukocytes, also called white blood cells , which are immune cells, with other leukocytes or body cells...
typed by mixing them with serum
Blood serum
In blood, the serum is the component that is neither a blood cell nor a clotting factor; it is the blood plasma with the fibrinogens removed...
containing the anti-HLA antibodies. If the antibodies recognize their epitope
Epitope
An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The part of an antibody that recognizes the epitope is called a paratope...
on the MHC then complement
Classical complement pathway
The Classical pathway of activation of the complement system is a group of blood proteins that mediate the specific antibody response. The main activators of the Classical Pathway are antigen-antibody complexes.-Initiation:...
activation occurs and the cell will be osmotically lysed
Lysis
Lysis refers to the breaking down of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a "lysate"....
. Lysis results in the cell taking up a dye (trypan blue
Trypan blue
Trypan blue is a vital stain used to selectively colour dead tissues or cells blue. It is a diazo dye.Live cells or tissues with intact cell membranes are not coloured. Since cells are very selective in the compounds that pass through the membrane, in a viable cell trypan blue is not absorbed;...
). This allows identification of cell's MHC indirectly based on the specificity of the known antibodies in the serum.
External links
- How Preimplantation tissue typing works, HFEA website
- http://www.stanford.edu/dept/HPS/transplant/html/tt_1.html
- http://www.bchealthguide.org/kbase/topic/medtest/hw40261/descrip.htm