Immune antibodies occur in the serum of individuals who become sensitized to foreign antigens through pregnancy or transfusion.
- IgM predominates in the primary response, IgG in the secondary response.
- Most react at 37°C and are considered clinically significant.
- Examples include antibodies in the Kell, Rh, Duffy, and Kidd systems.
Immune antibodies can be classified as alloantibodies or autoantibodies.
Alloantibodies
- Produced by exposure to foreign red cell antigens which are non-self antigens but are of the same species.
- They react only with allogenic cells.
- Exposure occurs through pregnancy or transfusion.
- Examples include anti-K and anti-E.
Autoantibodies
- Produced in an autoimmune process and directed against one's own red cell antigens.
- React with patient's own cells and all cells tested.
- Can possibly mask the presence of other significant antibodies.
- It is very important to make sure that no underlying significant antibodies are present if an autoantibody is suspected.
- A positive direct antiglobulin test (DAT) or auto control could indicate the presence of an autoantibody.
- Examples include cold auto (P or I) or warm auto (Rh specificity).
