Normally an animal will not have antibodies against antigens present on the surface of its own red blood cells or against blood group antigens of that species unless they have been produced following pregnancy, a previous transfusion or a [[Vaccines|vaccine]] reaction. However this is not the case for cats, who have naturally occurring alloantibodies. | Normally an animal will not have antibodies against antigens present on the surface of its own red blood cells or against blood group antigens of that species unless they have been produced following pregnancy, a previous transfusion or a [[Vaccines|vaccine]] reaction. However this is not the case for cats, who have naturally occurring alloantibodies. |