Having been a Medical technologist for about eighteen years, I have some knowledge and experience concerning Serology and Immunohematology. Serology is a biological science which studies antibody-antigen reactions in serum. Serum could be defined as the pale yellow liquid which separates from whole blood once it is clotted and spun down in the lab Serological testing can take place in many ways, depending on which antibody is being tested for. Some of the methods include: ELISA, agglutination, precipitation and fluorescent antibody techniques. Immunohematology (also known as Blood Banking) is the science which uses blood and serum to identify problems which may occur in a cross-match, compatibility which needs to be checked, before blood can be transfused from one person to another.
So these two branches of Medical Technology are very much intertwined. Various serological tests performed in the lab are necessary before blood can be used for a transfusion. Blood must first be checked serologically for HIV, hepatitis and other blood borne diseases. This is usually done in the Serology lab. Immunohematology tests include blood grouping, where blood types are tested to see if the donor and recipient are ABO and Rh factor compatible.
The techniques of testing blood groups originally stem from the testing for antigen-antibody reactions in serum. Because of these early methods of serological testing, the more complicated techniques of transfusion therapy with cells and plasma were developed. Techniques used in serology have also helped identify incompatibility reactions, an especially important one being, erythroblastosis fetalis, or hemolytic disease of the newborn. This disorder is due to the Rh incompatibility between mother and child, and could spell dire consequences for the baby.
Dire consequences can also occur in blood transfusions themselves. Although there is no danger to the person donating the blood, the recipient can be at risk. Because of this, additional antibody-antigen tests may need to be performed. A patient's history is also very important in these cases. People who have had multiple transfusions over the years may have minor antigens present on their red blood cells which they are not aware of.
Serological testing may also be used to determine immunodeficiencies. One such disorder, called X-linked (because it is linked to the X chromosome that was inherited) agammaglobulinemia is a genetic disease where a person does not have any immunity and can not fight off infections. Because a person with this disorder cannot produce antibodies, a special test called a Western Blot is needed to diagnose them.Treatment for these people is a once a month injection of immunoglobulin for the rest of their lives. So they are essentially receiving human IgG antibodies. Again, since IgG is made of human plasma, many tests must be performed before infusion can take place.
So you can see that Immunohematology is a part of laboratory Serology as well as an extension of it, one that is very important to the health and longevity of humans.