Question

if blood types do not match in a transfusion, the new blood cells may be attacked by produced by the recipients immune system.

Explanation:

Step1: Recall blood transfusion immune response

In blood transfusion, when blood types don't match, the immune system reacts.

Step2: Identify immune component

Antibodies are proteins produced by the immune system to attack foreign substances. In mismatched blood transfusion, the recipient's immune system produces antibodies against the foreign blood cells.

Answer:

antibodies