Tissue typing

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 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.

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