Mixtures Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Mixtures and links to relevant pages within the course.
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| The History of the ABO System (cont.) Landsteiner, knowing that none of his subjects had been immunized, realized that “natural” antibodies must develop which are directed against antigens not present on the red cells. Individuals with “A” antigens on their red cells had sera containing “Anti-B” antibody. Individuals with “B” antigens had sera containing “Anti-A.” “AB” individuals had sera with no ABO antibodies present and “O” individuals’ sera contained “Anti-A” and “Anti-B.” Sera from group O individuals may contain a separate antibody, “Anti-A,B.” Anti-A,B possesses serologic activity not found in mixtures of Anti-A and Anti-B. Anti-A,B sera will agglutinate A, B, and AB cells. It is particularly useful in detecting weak A and B antigens. See the table on the next page. | View Page |
| Agglutination Reactions Antibodies of the ABO system cause agglutination of saline-suspended red cells at 4°C to 20°C. Heating to 37° weakens the reaction. “Naturally” occurring ABO antibodies may not be strong enough to agglutinate cells without centrifugation. Thus, testing serum for the presence of anti-A or anti-B has classically been performed using the tube system in which serum and cells added to a test tube are centrifuged and then evaluated for agglutination. A slide test has also been performed for forward reactions. Although tube tests are still in wide use, newer systems utilizing other technology such as gel agglutination are becoming more prevalent. The image on this page illustrates agglutination reactions observed with the tube system, from 4+ in the topmost image, to 0 in the lowest image. ABO reactions should be strong. Weak or missing reactions occur, but must be "resolved" before blood products can be released.4+ agglutination: Red blood cell button is a solid agglutinate; clear background.3+ agglutination: Red blood cell button breaks into several large agglutinates; clear background.2+ agglutination: Red blood cell button breaks into many medium-sized agglutinates; clear background; no free red blood cells.1+ agglutination: Red blood cell button breaks into many small clumps barely visible macroscopically; background is turbid; many free red blood cells.Negative: No agglutinated red blood cells present; red cells are observed flowing off the red blood cell button during the process of grading.Other reaction which may occur are the mixed-field reaction, in which mixtures of agglutinated and unagglutinated red blood are present; and hemolysis, in which red cells are hemolyzed by the antibody. Both of these patterns are considered positive reactions. | View Page |