Final answer:
When a person receives a transmission of a different blood type, their antibodies can react with the foreign antigens on red blood cells, causing them to clump together. A cross-match assay is performed before a transfusion to ensure compatibility between the donor and recipient.
Step-by-step explanation:
The positive tests you saw are similar to what happens to a person's blood when he or she receives a transmission of a different blood type. Blood types are determined by the presence or absence of certain antigens on red blood cells. For example, the ABO blood type system includes four types: A, B, AB, and O. When someone with type A blood receives a transfusion of type B blood, their antibodies will recognize the foreign B antigens and cause the red blood cells to clump together, potentially leading to a transfusion reaction. Similarly, in the Rh antigen system, a person who is Rh negative can have a reaction if they receive Rh positive blood.
In medical settings, a cross-match assay is performed before a transfusion to ensure compatibility between the donor and recipient. This involves mixing a small aliquot of the recipient's serum with the donor's red blood cells. If agglutination occurs, indicating a reaction, it means that the recipient has antibodies against the donor's blood cells, and the transfusion should be avoided.