Final answer:
The study and diagnosis of antigen-antibody interactions in the blood is called C) serology. It involves analyzing blood serum and the immune system's response to pathogens. Immunohematology is related but specifically examines the interplay between blood components and the immune system.
Step-by-step explanation:
The study and diagnosis of antigen-antibody interactions in the blood is known as serology. Serology involves the examination of blood serum, specifically the response of the immune system to pathogens as evidenced through the presence of specific antibodies. In contrast, immunohematology is a subfield of hematology which focuses on the study of blood and blood-forming tissues in relation to the immune response. Blood types are distinguished based on the presence or absence of specific antigens on the surface of red blood cells, such as those named by the ISBT.
Blood-group antigens, which include proteins like immunoglobulins (IgG, IgM, IgA, IgD, IgE), are recognized by B-lymphocytes and can result in responses such as agglutination, exemplified by hemagglutination. Hemagglutination is used in assays like the direct Coombs' test to detect antibodies that don't cause agglutination and the presence of complement attached to red blood cells. The complex nomenclature of blood-group antigens, including blood types defined by antigens, has evolved with efforts to standardize it by institutions like the ISBT, although inconsistencies remain.