Why does a patient's body accept the blood by transfusion despite the fact that the immune system tends to reject foreign objects?

Answer 1

To learn the answer of the above question first we have to know about the blood characteristics.There are four major types of blood A, B, AB, and 0. The blood types are determined by proteins called antigens. This antigen is found on the surface of the Red Blood Cell (RBC). Basically there are two antigens, A and B. If you have the A antigen on the RBC, then you have type A blood. When B antigen is present, you have type B blood. When both A and B antigens are present, you have type AB blood. When either are present, you have type O blood. When an antigen is resent on the RBC, then the opposite antibody is present in the plasma. For instance, type A blood has anti-type-B antibodies. Type B blood has anti-type-A antibodies. Type AB blood has no antibodies in the plasma, and type O blood has both anti-type-A and anti-type-B antibodies in the plasma. These antibodies are not present at birth but are formed spontaneously during infancy and last throughout life. In addition to the ABO blood group system, there is an Rh blood group system. There are many Rh antigens that can be present on the surface of the RBC. The D antigen is the most common Rh antigen. If the D antigen is present, then that blood is Rh+. If the D antigen is missing, then the blood is Rh-. Blood is transfused to a patient after determining the blood group and matching the characteristics of both. In such case the immune system accepts the foreign object.