What technique is used to remove antibody bound to sensitized red blood cells?

• A. Adsorption
• B. Precipitation
• C. Neutralization
• D. Elution

Answer: (D)

Elution is the technique used to remove antibody bound to sensitized red blood cells. When red cells are coated with IgG in vivo, a direct antiglobulin test (DAT) can be positive. To identify which antibody is bound, the bound IgG is released from the cell surface into solution by an elution procedure (commonly acid treatment, which lowers the pH to disrupt antigen–antibody interactions). The eluate containing the released antibody is then tested against a panel of red cells to determine its specificity. This process helps distinguish the antibody causing the coating and is particularly useful for identifying alloantibodies when an autoantibody or mixed-field reactivity is present. Adsorption, precipitation, and neutralization involve different mechanisms or aims and do not detach bound antibody from the red cell surface.