IMMUNOLOGY

Detailed explanation-1: -Landsteiner explained that the reactions between the RBCs and serum were related to the presence of markers (antigens) on the RBCs and antibodies in the serum. Agglutination occurred when the RBC antigens were bound by the antibodies in the serum.

Detailed explanation-2: -Agglutinogens are glycoproteins present on the surface of red blood cells. Blood grouping is based on two types of agglutinogens that are responsible for the four types of blood groups-A, B, AB and O. A person with blood group A has A agglutinogen.

Detailed explanation-3: -Blood type AB has both A and B surface antigens, and neither anti-A nor anti-B antibodies circulating in the plasma. When anti-A antibodies (added to the first well) contact A antigens on AB erythrocytes, they will cause agglutination.