Antibodies

An antibody is a product of an antibody immune response and will react with that antigen in some observable way. Antibodies are immunoglobulins (Ig) immunoglobulins and are found in the gamma globulin part of plasma proteins.

There are five categories of immunoglobulins: IgG, IgM, IgA, IgD and IgE.

Blood group antibodies

These are usually produced when an individual is exposed to blood of a different group by transfusion or pregnancy (‘alloantibodies’). 

This is a particular problem in patients who require repeated transfusions, for conditions such as thalassaemia or sickle cell disease, and can cause difficulties in providing fully compatible blood if the patient is immunised to several different groups. 

Some antibodies react with red cells around the normal body temperature of 37°C (warm antibodies). Others are only active at lower temperatures (cold antibodies) and do not usually cause clinical problems although they may be picked up on laboratory testing.