278 ' IMMUNOLOGY 



The Dicks report statistics that indicate a very high percent- 

 age of efficiency for the susceptibility test. 



Prophylactic Immunization. — In regard to the value of prophy- 

 lactic immunization against scarlet fever, there is much disagree- 

 ment. The results reported by the Dicks are apparently quite 

 definite. They observed no cases of scarlet fever among 1,191 

 susceptible interns and nurses who had been immunized with 

 toxin whereas they noted 37 cases of scarlet fever in a control 

 group. Hektoen and Johnson (1934) report statistics from the 

 Durand Hospital which support the findings of the Dicks. There 

 are at present a great many who report results at variance with 

 those just cited. Zinsser, Enders and Fothergill (1939) suggest 

 that active immunization with the Dick toxin may be of value 

 among nurses and interns but do not recommend large scale im- 

 munization as a part of a public health program. 



The Dick Test and Toxin Valency. — While a negative Dick 

 test indicates a certain amount of immunity to the toxins of scarlet 

 fever streptococci, it is not a measure of immunity to infection 

 with the organisms. It has been shown by Kirkbride and Wheeler 

 (1924) and others that hemolytic streptococci isolated from cases 

 of erysipelas are able to produce scarlet fever toxins. Downs and 

 Stookey (1932) have shown that hemolytic streptococci from cases 

 of puerperal sepsis produce toxins indistinguishable from those 

 produced by scarlet fever streptococci. Similar results have been 

 obtained for hemolytic streptococci from a number of pathologi- 

 cal conditions (Wadsworth, 1934). Furthermore, Wheeler (1932), 

 Wadsworth (1934), Trask and Blake (1933), and others have 

 called attention to antigenic differences in the toxins of scarlet 

 fever streptococci. Antitoxin specific for one strain may not 

 neutralize the toxin produced by another. 



Since scarlet fever streptococci are of "questionable specific- 

 ity," Zinsser and Bayne-Jones (1939) recommend that strains 

 that possess as great an antigen valency as possible be selected 

 for toxin production. They call attention to the Dochez N Y 

 5 strain which produces a toxin of "great antigenic valency." 

 The Dicks have used a polyvalent toxin; i.e., one prepared by 

 mixing the toxins of several strains to meet this requirement. 



