378 IMMUNOLOGY 



determining specificity is illustrated when one employs antigens 

 having a common protein fraction and differing only in that their 

 haptens are stereoisomers of each other. Thus when dextro-, Icvo-, 

 and meso-tartaric acids are attached respectively to pig serum, 

 three different antigens are formed. An antibody can be pro- 

 duced for each of these antigens lliat Avill not react with either of 

 the other two. 



Landsteiner's Method of Producing- New Conjugated Anti- 

 gens. — In order that the student may appreciate the significant 

 work of Landsteiner on conjugated antigens, a brief discussion 

 is given of the method he employs in introducing chemical groui)s 

 (haptens) into an antigen. The discussion calls attention to the 

 importance of these aromatic amino acids that have an OH group 

 attached to the benzene ring in preparing a conjugated antigen. By 

 first diazotizing the compound, the hapten can be linked to the 

 nucleus replachig a hydrogen adjacent to the OH group. It is 

 suggested also that linkage of the hapten with the salt-forming 

 groups may occur. Specific antibodies representing each hapten- 

 protein antigen can be produced. 



Suggested Explanation of Drug Allergy. — Since it has been 

 shown tliat an animal's own protein when modified by the addition 

 of a hapten will stimulate antibodies if injected into the same 

 animal, it has been suggested that some of the drug allergies oc- 

 cur when the drug, or some portion of it, acts like a hapten and 

 unites with the patient's proteins and forms an antigen capable 

 of stimulating antibody formation and sensitization of the patient. 



Mosaic Structure of Antigens. — As one contemplates the pos- 

 sible significance of all these facts about antigens, one can appre- 

 ciate ])erliaps tlie significance of Landsteiner's suggestion that 

 antigens may have a mosaic structure. It is recommended tlmt 

 the student read Landsteiner's monogry])h on "The Specificity of 

 Serological Reactions" (1936). 



