Sera Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Sera 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 |
| Table 2: Testing the Patient Red Cells with Known Antisera (Forward Typing) In routine practice, specially prepared blood grouping sera containing anti-A, anti-B, (and optionally anti-A,B) are used to identify the four types of red cells. These sera will agglutinate cells with the corresponding antigen. This is called forward typing. ABO Blood Group Patient Red Cells Tested with Known Antisera Anti-A Anti-B Anti-A,B A 4+ 0 4+ B 0 4+ 4+ O 0 0 0 AB 4+ 4+ 4+ + = agglutination (graded 1+ to 4+)0 = no agglutination | View Page |
| Table 3: Testing the Serum with Known Red Cells (Reverse Typing) It has been demonstrated that antibodies occur predictably in the sera of all normal adults in association with the ABO antigens. Demonstration of these antibodies is therefore necessary for definitive classification of an individual’s ABO cell type. The individual’s serum is therefore tested against reagent red cells containing known antigens. Patient ABO Blood Group Patient Serum Tested with Known Reagent Cells A Cells B Cells A 0 4+ B 4+ 0 O 4+ 4+ AB 0 0 + = agglutination (graded 1+ to 4+)0 = no agglutination or hemolysis | View Page |
| ABO Antibodies and Aging ABO antibodies are not usually produced by an infant until 3 to 6 months of age. Antibodies found in the sera of newborns are almost always IgG, passively acquired from the mother. Thus, serum testing of newborns is not performed. Anti-A and anti-B titers are highest at ages 5-10 years and then they gradually decrease. Thus, in elderly patients, ABO antibodies may be difficult to detect. In patients with hypogammaglobulinemia, some leukemias, lymphomas or patients who are taking immunosuppressive drugs, the expected antibodies may be weak or even absent, reflecting the low levels of gamma globulin in the patient’s serum. As previously mentioned, these and other ABO typing discrepancies must be resolved before true ABO type can be determined. | View Page |
| A1 and A2 The most common classifications are A1 and A2. These account for over 99% of group A bloods. Of this 99%, A1 compromises approximately 80%. Commercial anti-A typing serum does not differentiate between A1 and A2 cells. A1 cells contain “A” antigen and “A1” antigen. A2 is not really a unique antigen. It is thought to be simply “A” antigen with no “A1” antigen. Several preparations are available that will react with A1 cells, but not other subgroups of A. An extract of the seeds of the plant, Dolichos biflorus has specific anti-A1 activity. “Absorbed anti-A” serum can also be prepared. To do this, the anti-A from group B people is absorbed with A2 cells. Anti-A is removed and a second antibody that reacts only with A1 cells remains. Anti-A1 can also be found as a separate antibody in the sera of A2 and A2B individuals. | View Page |