412 Microbes and You 



and B serum, or anti-A and anti-B serum, and the operator must 

 be certain of the type of sera with which he is working. Type A 

 serum is obtained from a person who has type A blood cells, and 

 such serum causes clumping of type B cells. But anti-A serum is 

 produced by injecting animals, usually rabbits, with type A cells, 

 and the injected laboratory animal builds up antibodies which 

 cause agglutination of type A cells. The same principle holds 

 true with type B serum and anti-B serum. 



To conduct the slide test, an ordinary microscope slide is 

 marked off with two circles about the size of a five cent piece. 

 The left hand circle is labeled "A" and the right hand circle is 

 marked "B." A fair-sized drop of a saline suspension of blood 

 cells is introduced into each of the circles. Assuming that specific 

 antisera are going to be employed in the typing procedure, place 

 a drop of anti-A serum in the left circle and a drop of anti-B 

 serum in the right circle. With the aid of a toothpick, mix the 

 contents of the left circle thoroughly, then turn the toothpick 

 around and mix the contents of circle B. 



With a rotary motion of the slide, carefully agitate the cell 

 suspensions for a minute or two making certain that the contents 

 of the two circles are not allowed to come in contact with each 

 other. Visible clumping of the erythrocytes will take place if the 

 antiserum is specific for the cells. By employing such antisera, the 

 following reactions will occur: 



Type A blood will be clumped only by anti-A serum (left 

 circle ) . 



Type B blood will be clumped only by anti-B serum (right 

 circle ) . 



Type AB blood will be clumped by both anti-A and anti-B sera 

 (both circles). 



Type O blood will not be clumped by either antiserum (neither 

 circle ) . 



Macroscopic readings of these reactions should be confirmed 

 by microscopic examination of the preparations under low power. 

 Weak reactors may be visible only by use of the microscope. 



The test tube technic is more accurate than the rapid slide test, 



