Blood transfusion groups (1965) Pt. 1 of 2

uniform may make the men but it does not make men uniform as we all know there are variations in the human makeup one of the most important of these is in the blood for a patient undergoing a blood transfusion identifying and then using the right variety of blood may make the difference between life and death if blood mixed with an anticoagulant is left to stand it separates into two parts the red cells settle at the bottom leading above them the fluid part called plasma without an anti-coagulant the blood clots and the fluid which separates is now called serum in the case of a transfusion if the red cells from one person are mixed with a serum from another person the results can indicate either safety or danger for the patient in a correctly matched mixture the red cells of the recipient will stay apart the result we wish to achieve in an incorrectly matched mixture the red cells may agglutinate that is clumped together or they may be entirely lysed that is dissolved both these reactions indicate danger to the patient before 1900 a blood transfusion was a hit or miss operation often the patient reacted unfavorably to the transfusion sometimes with fatal results the viennese scientist landsteiner was the first to devise tests which divided human blood into four groups these groups are called group o today distinguished by a blue label group a with a yellow label group b with a pink label and group a b with a white label landsteiner recognized that the dangerous reactions to a transfusion were caused by chemical substances called antibodies in the blood plasma or serum reacting against antigens different chemical substances carried on the surfaces of the red cells we can show this in a diagram but in fact antigens and antibodies are far too small to be visible under the microscope if transfused blood is not correctly matched the antibodies in the patient's serum anti-a anti-b or both will react against antigens of the same letter carried on the donors red cells group o red cells do not carry a or b antigens and thus are not affected by anti a or anti b antibodies group a red cells are agglutinated by anti-a antibodies group b by anti-b antibodies and group a b are agglutinated by both anti-a and anti-b where do the antibodies come from landsteiner discovered that they occur in the sierra of people thus group o serum contains both anti-a and anti-b group a serum contains only anti b group b serum contains only anti a whilst group a b contains nothing but if we investigate red cells more closely we find that besides a and b antigens their surfaces carry a whole series of other antigens varying in different people to take a theoretical example if red cells carrying an antigen let's call it x are transfused into a patient whose red cells lack this antigen x the patient may develop antibodies against the x intruder a later transfusion of blood carrying antigen x will be attacked by these antibodies and may cause a severe and possibly fatal reaction