a transfusion. Blood cross-matching mixes patient’s serum with donor red blood cells to see if there is a reaction.
EIAS AND ELISA TESTING Enzyme immunoassays or EIAs will use antibodies in order to check for antigens in the patient’s serum. They are done on microtiter plates or done in vivo. The antibody interacts with an enzyme that can do a specific reaction, which can be detected. Often the enzyme is a chromogen that is turned into a colored product that can be detected. Others are attached to fluorogens that will be converted into a fluorescent form after a reaction occurs. EIAs can be used in immunostaining. This is used to look at whole tissues that are stained with monoclonal antibodies. Immunocytochemistry is related to immunohistochemistry testing but it strips away the extracellular membrane and makes the cell membranes of tissues permeable to antibodies so antibodies can be detected against organelles and proteins within the cell. This can involve a color-changing enzyme or a fluorescent staining technique. The ELISA tests or the enzyme-linked immunosorbent assays are commonly used EIA tests. There is a direct ELISA that involves antigens immobilized inside a well on a plate. Specific antibodies are added to look for an antigen. If the antigen-antibody complex exists, a color-changing enzyme will be used to look for the existence of the complex. The sandwich ELISA test will quantify the amount of the antigen in the solution. The antigen can be anything, such as a serum protein, hormone, or pathogenic antigen. A primary antibody is added to the wells, with the unbound antibody washed away. A blocking protein is then added to bind nonspecific antibodies in the well. Then a secondary polyclonal antibody is added that is attached to an enzyme. If there is a complex formed, there will be a colored end product. The actual amount of color found is detected with a spectrophotometer so the antigen can be quantified. Indirect ELISA testing quantifies the antibody instead of an antigen. It can detect antibodies to HIV disease and Lyme disease. The test affixes a known antigen to a well 245
