CHAPTER XXIV 



PRECIPITIN TESTS IN SYPHILIS 



Introduction. — Many precipitation tests applicable to syphilitic 

 seniin have been proposed since the observation by INtichaelis 

 (1907) of a precipitate when heated syphilitic serum and lipoidal 

 tissue extracts were mixed. Tliis method lias l)een described by 

 various authors as a precipitation, floccvilation or a clarification 

 reaction. In the serum of syphilitics thei-e is usually present an 

 antibodj^-like substance, reagin, which is directly or indirectly 

 responsible for chanoes in the dispersion of the lipoidal antigens. 

 These aggregates may vary in size from small microscopic to large 

 macroscopic clumps. In normal human serum reagiu is rarely 

 present, hence the ''reagin-lipoid" complex cannot be formed. 

 Thus there is no increase in the size of the dispersed particles of 

 lipoidal suspension. The precipitation tests, like complement 

 fixation methods, are a qualitative or a quantitative estimation of 

 "reagin" resulting from the infection and not a test for the pres- 

 ence of the causative oi-ganism. 



Historical Development. — The successful development of the 

 precipitation methods began with the work of Sachs and Georgi, 

 and Meinicke, hence their practical application has been within 

 the last twenty years. It is of historical interest to note that the 

 first attempt to apply precipitation methods followed the Was- 

 sermann, Neisser and Bruck (1906) complement fixation method 

 by one year. Michaelis (1907) using the Wassermann antigen 

 originated this early test, believing he was using a specific extract 

 of spirochetes and securing a specific jn-ecipitin test for the 

 spirochete. This was followed by Klau.sner's (1908) method of 

 precipitation with distilled water and the taurocholate suspensions. 

 These early precipitation tests were macroscopic test tube reac- 

 tions. 



Introduction of Cholesterol. — Jacobstahl made a long step 

 forward by introducing an alcoholic extraction of syphilitic liver 

 as an antigen in place of the lipoid-poor saline extracts. His test 

 was also the first microscopic reaction. This test depended upon 



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