748 TOXINS, TOXOIDS, AND ANTITOXINS 



given, as the percentage of pseudo-reactions is considerably increased due to the 

 repeated previous injections of the toxin and its accompanying products. 



PREPARATION OF TOXIN-ANTITOXIN 



In preparing the toxin-antitoxin mixture for active immunization against diph- 

 theria of those individuals showing a positive Schick test, an aged toxin is used. Dur- 

 ing the aging of the toxin, about one-half to two-thirds of the toxin is modified into 

 toxoid and the L+ becomes stabilized. 



The toxin selected should contain at least five L4- doses to each mil. The anti- 

 toxin used for the partial neutralization of the toxin is purified by concentrating 

 methods and should contain at least 2,000 units of antitoxin to each mil. The toxin 

 is prepared in batches of 16-20 liters. Each toxin batch should be uniformly mixed 

 before being stored for aging. The o.i L4- toxin-antitoxin mixture is made up in 

 40-liter preparations. To prepare the 40 liters, 800 mils of toxin (containing five L+ 

 doses to each mil) are placed in a 2-liter flask and 3,000 units of diluted antitoxin 

 are added. These are mixed and added to the diluent of 0.8 per cent salt solution 

 containing 0.5 per cent phenol, again thoroughly mixed and filtered through a 

 Berkefeld candle. It is then injected into guinea pigs to test its active immunizing 

 value and to determine if the preparation is properly balanced. For this purpose, a 

 series of guinea pigs is injected. In each series the following amounts are given 

 (the degree of toxicity as illustrated is that of a properly balanced mixture which will 

 give a high percentage of immunes in susceptible individuals) : 



J mil — no symptoms 



^ mil — slight paralysis after eighteen days followed by recovery 



I mil — paralysis appearing in fourteen to twenty days; death due 



to complete paralysis in twenty to thirty days 

 5 mils — death in four to seven days 



The active immunizing value of the mixture is determined by injecting the surviv- 

 ing guinea pigs with B. diphtheriae toxin. Five weeks should elapse before the pigs are 

 tested. The series which received the j-mil amounts should withstand the injectioa of 

 five M.L.D.'s; those which received the | mil should withstand ten M.L.D.'s. Occa- 

 sionally a guinea pig which has received the i-mil dose will recover after almost com- 

 plete paralysis. These animals will withstand twenty to twenty-five M.L.D.'s. A tox- 

 in-antitoxin mixture giving the foregoing results is released for active immunization in 

 humans. The amount injected in humans for active immunization is i mil at weekly 

 intervals for three doses. About 90 per cent of the individuals become immune within 

 three to four months. To ascertain if the individual responded to the treatment and 

 is immune, a Schick test should be done four to six months after the toxin-antitoxin 

 injections. To those who still give a Schick positive test, a second series of toxin- 

 antitoxin injections must be given. It should be continually emphasized that no 

 certificate of immunity should be given until a Schick negative test results. 



TOXIN-ANTITOXIN SUBSTITUTE FOR THE SCHICK TEST 



Advantage has been taken of the toxicity (see above) in the toxin-antitoxin 

 preparations by Dr. W. H. Park. He introduced the method of using the first injec- 



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