IMPORTANCE OF ANTIBODIES IN DIAGNOSIS 385 



with typhoid vaccines. The last named authors find both agglu- 

 tinins produced contrary to the conclusions of Felix who held that 

 only "H" agglutinins were formed as a result of vaccination, while 

 "0" agglutinins were produced by infection. In a series of in- 

 dividuals who were immunized against typhoid, the "H" ag- 

 glutinin titer was much higher than the " 0, " the former showing a 

 pronounced steady drop from an average titer of 1 :95 for 20 

 weeks after the last injection followed by a more gradual decrease 

 in titer until a titer of about 1 :80 was reached in 140 weeks. The 

 " " agglutinations reached, on an average, a titer of only 1 :80 

 and fell during the same period of time to approximately 1:40. 



Effect of Allergy on Ag-g-lutinin Titer. — Lamson and Kessel 

 (1932) noted low titers in a group of allergic individuals given 

 multiple injections of typhoid vaccine. They assumed that im- 

 munity was produced in spite of the low antibody response. In- 

 quiry should always be made of patients who are suspected of 

 having typhoid fever to ascertain whether they have been vac- 

 cinated with a typhoid vaccine, since an increase in titer would be 

 expected in such individuals. 



Experimental Results on Agglutinin Variation. — The result of 

 vaccinating a large series of rabbits, some being given 'one in- 

 jection while others are given two, three or more injections, is 

 quite surprising in that a wide variation in response is found. 

 Some animals are very poor antibody producers, while others 

 yield exceptionally high titers. If only one injection is given 

 to an animal which produces antibodies readily the titer viaj/ 

 change from zero on the day of vaccination to 1 :500 or 1 :700 

 on the fifth to seventh day, although often it is less. The con- 

 centration of antibody rarely continues to rise longer than the 

 tenth day and frequently is dropping by that time to reach a low 

 level in from three to six weeks. Where several injections of a 

 vaccine are given, it is customary to administer them at from 

 three- to seven-day intervals. This is done to keep the antibody 

 titer rising. As a rule there is a slight drop in titer after each 

 injection, followed by a fairly sharp rise during the next few 

 days. 



Time of Appearance of Maximum Titer.- — The maximum titer Is 

 usually attained after four to six injections and is reached usually 

 five to seven days after the last injection. 



