What are anti
They have the ability to recognize bacteria and viruses by attaching to unique structures (antigens) on the surface of the bug that identify it as an invader.
The immune system only makes antibodies for a specific antigen if it encounters it during its surveillance of the body’s tissues.
Anti K antibodies, for example, bind to the ‘Kell antigen’ on red blood cells. The antibodies are usually made after a blood transfusion, when the Kell antigen encountered by your immune system is not your own.
People with anti K antibody in their blood are most unlikely to come to any harm by it being there.
The antibodies often disappear over time. If you were to require surgery, the anti K antibody in your blood would be detected prior to the operation and blood without Kell antigen would be given if necessary.