haemagglutination - أطلس مختبرات العرب

The active haemagglutination test (upper panel, left) detects antibodies to red blood-cell antigens. The antibody is serially diluted (usually in doubling dilutions) in physiological saline and placed in the wells (columns 1–10, lower panel read left to right) of the haemagglutination plate. Positive controls (column 11) and negative controls (column 12) are included. In this example, eight different antisera (rows A–H) are being tested. A suspension of red cells (containing a protein to prevent the red cells agglutinating non-specifically) is added to each well to give a final concentration of about 1% cells. If sufficient antibody is present to agglutinate (cross-link) the cells, they sink as a mat to the bottom of the well. If insufficient antibody is present, the cells roll down the sloping sides of the plate to form a red pellet at the bottom. Some antibodies do not agglutinate red cells very effectively and may be detected in the indirect agglutination test by the addition of a second antibody which binds to the non-agglutinating antibody already bound on the red cell. By binding different antigens onto the red-cell surface, covalently or non-covalently, the test can be extended to detect antibodies to antigens other than those found on red cells (upper right panel). Chromic chloride, tannic acid, glutaraldehyde and a number of other chemicals are used to cross-link the antigen to the cells.