Naturally occurringantibodies occur in the plasma of individuals who lack the corresponding antigen and who have not been pregnant or transfused. The most important are anti-A and anti-B. These are usually IgM antibodies.
Immune antibodies develop in response to the introduction of red cells possessing antigens the individual lacks. This may occur after pregnancy or previous blood transfusions. These antibodies are commonly IgG optimally react at 37 C. One example is anti-D.
Detection of Immune Antibodies
A) Direct Anti-globulin/Coombstest
Aim: Detects antibody or complement on the red cell membrane
Dispense 1drop of red cell into a test tube
Wash red cells 3-4 times with saline (To remove unattached antibodies)