QUALITATIVE IMMUNE RESPONSES 



diphtheria toxoid, in the same species, man. In normal 

 persons purified diphtheria toxoid given subcutaneously 

 provokes the appearance of antitoxin in the blood and with 

 two or more doses a high enough titre may be obtained to 

 allow demonstration of flocculation with antigen. Con- 

 comitantly the individual becomes S chick-negative and is 

 immune to symptomatic infection by Cory neb acterium 

 diphtheriae. 



In some individuals, however, a different result is obtained. 

 Kuhns and Pappenheimer (1952) describe a child who 

 suffered an acute asthmatic reaction after a 'booster' inocu- 

 lation of diphtheria toxoid. Investigation showed that 

 a minute dose of purified toxoid injected intradermally 

 provoked an immediate wheal and flare reaction of the type 

 seen with pollen extract in a hay-fever subject. The serum 

 contained 50 units of antitoxin by rabbit skin titration but 

 failed to flocculate with toxin. This led to the examination 

 of a large number of subjects and several more examples of 

 this non-flocculating antitoxin were found. Antitoxic serum 

 of this type can be used to transfer skin hypersensitivity to the 

 skin of a normal individual (Prausnitz-Kustner reaction). 

 It fixes complement only in the presence of a high concentra- 

 tion of serum. It does not precipitate with toxin or toxoid, 

 but co-precipitates when antigen and normal precipitating 

 antitoxic serum are added. 



There are other examples where a single antigen can, 

 depending on circumstances, give either classical antibody 

 production or a delayed type of hypersensitivity analogous 

 to the tuberculin reaction. Dienes (1929) and Raffel and 

 Forney (1948) showed that, by providing appropriate 

 cellular environments, antigens like ovalbumin could be 

 made to induce tuberculin type hypersensitivity to intra- 

 dermal injection of the antigen. There is much to suggest that 

 in addition to these examples there are common features in 

 skin sensitization to simple chemicals like picryl chloride and 

 in homograft immunity. In all cases passive transfer with 



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