Final answer:
The term describing a protein on blood cells that causes incompatibility reactions during blood transfusions is 'antigen'. These reactions are part of a type II hypersensitivity response, where antibodies bind to the antigens causing cell lysis and potential severe health consequences.
Step-by-step explanation:
The general term describing a protein on blood cells that causes incompatibility reactions is antigen. These antigens may be proteins, carbohydrates, lipids, or nucleic acids that are recognized as foreign by the recipient's immune system during a blood transfusion. If a person receives incompatible blood, their immune system produces antibodies that bind to the antigens on the infused erythrocytes, leading to agglutination and cell lysis. This is known as a hypersensitivity reaction, specifically type II hypersensitivity, which can have severe consequences such as a hemolytic transfusion reaction (HTR). In some cases, like erythroblastosis fetalis or autoimmune diseases, these reactions are against the body's own cells.