A sample of blood from a mismatched transfusion is observed under the microscope. many large clumps of erythrocytes are observed. which is the antibody responsible for this?

I believe the antibody responsible for this is IgM. Antibodies are protective proteins produced by the immune system in response to the presence of a foreign substance called, antigen. They recognize and latch onto antigens in order to remove them from the body. IgM is the most abundant antibody that is found in all body fluids and protects against bacterial and viral infections. The IgM that is found mainly in the blood and lymph fluid is the first antibody to be made by the body to fight a new infection.