Blood typing relies upon which type of interaction?

• A. relies upon the specific interaction between antibodies against various antigens on the surface of RBCs
• B. uses PCR to detect DNA sequences
• C. measures white blood cell count
• D. is based on the pH of serum

Answer: (A)

Blood typing relies on the specific interaction between antibodies in antisera and antigens on the surface of red blood cells. When antisera containing antibodies against particular red-cell antigens is mixed with a person's blood, those antibodies bind to the matching antigens if they are present, causing the cells to clump together (agglutinate). The pattern of agglutination reveals which antigens are present, allowing determination of ABO type and Rh status. This is a serologic test based on antigen-antibody binding, not a genetic test or a measurement of white blood cells or serum pH.