528 



COLLEGE ZOOLOGY 



tibodies in the recipient's serum have on 

 the antigens of the donor's red blood corpus- 

 cles? Thus it is possible, for example, to 

 give a type O blood transfusion to a type A 

 person, but the reverse, that is, giving type 

 A to a type O person, would cause a severe 

 reaction. 



The relation of antigen, antibody, and 

 blood group is summarized in the follow- 



ing table: 



BLOOD GROUP 



A 

 B 



AB 

 O 



ANTIGEN IN 

 ERYTHROCYTES 



A 



B 



AB 



None 



ANTIBODY IN 

 BLOOD SERUM 

 b 



a 



None 

 a and b 



Subgroups of the A-B-O blood groups have 

 been discovered in recent years, some of 

 which must be taken into consideration in 

 making blood transfusions, thus complicat- 

 ing the work of the blood specialist. 



The blood of individual anthropoid apes 

 is assignable to one of the 4 human groups; 

 for example, A and O have been found in 

 chimpanzees. This is evidence of a close 

 chemical relationship between the apes and 

 man. Blood groups are also known in the 

 rabbit, dog, and cattle, but none is identical 

 with a human type. 



Rh factor 



The Rh blood factor is another impor- 

 tant blood antigen found in man and 

 monkeys. About 86 per cent of the white 

 population of the United States have this 

 antigen, hence are called Rh-positive; the 

 remaining 14 per cent are without it and 

 are therefore Rh-negative. Since the dis- 

 covery of the Rh factor, it has been estab- 

 lished that there are no less than six differ- 

 ent antigens involved in the Rh system; of 

 these, however, only the Rh antigen is usu- 

 ally of serious clinical significance. 



There is no antibody that normally ac- 

 companies the Rh antigen as is true of the 

 antigens of the A-B-O blood groups. How- 

 ever, the Rh antigen will cause formation 

 of antibodies if the blood of an Rh-positive 



person is transfused into an Rh-negative per- 

 son. If at some subsequent time another 

 transfusion of Rh-positive blood is made to 

 this Rh-negative person, then the Rh an- 

 tigen reacts with the antibodies, causing a 

 serious transfusion reaction, agglutination, 

 which may result in death. 



Another serious result of Rh incompati- 

 bility may be caused when an Rh-negative 

 pregnant woman carries an Rh-positive 

 child. Rh-positive erythrocytes may pass 

 from the blood stream of the fetus into the 

 mother's blood, where they stimulate pro- 

 duction of antibodies (Fig. 420). These an- 

 tibodies of the mother may diffuse into the 

 blood stream of the fetus and cause destruc- 

 tion of fetal erythrocytes. This results in 

 varying degrees of injury to the fetus, de- 

 pending on the concentration (titer) of the 

 antibodies present. The effects range all the 

 way from a very mild anemia, scarcely de- 

 tectable, to more severe anemic conditions, 

 various structural abnormalities, abnormali- 

 ties of the nervous system, sometimes caus- 

 ing mental deficiency, to miscarriage or 

 stillbirth. 



There are many other blood groups such 

 as the P, M-N-S, Kell, Lewis, Lutheran, 

 Kidd, and Duffy. This is a field in which 

 there is much research activity, and new 

 blood group antigens are frequently found. 

 Since the presence of the antigens of one 

 blood group system is independent of an- 

 other, a person may have any one of many 

 possible different blood groupings. Con- 

 sidering all of these blood group systems, 

 the number of different blood type combi- 

 nations possible is well up in the millions, 

 which makes them useful in crime detection 

 and in determining the parentage of a child. 



Anthropologists have used the knowledge 

 of blood groups in the study of the relation- 

 ships of races. By a special technique it is 

 possible to determine the blood groups of 

 ancient bones and mummies. 



The inheritance of some of the blood 

 groups will be discussed in a later chapter on 

 heredity. 



