508 IMMUNOLOGY 



This product is now called Purified Protein Derivative or PFD. 

 The method of its manufacture is described in an excellent paper 

 by Reichell and Clark (1934). 



MA-100 OF Funk and Huntoon. — To prepare MA-100, a culture 

 is grown in Long's medium, rendered bacteria-free by filtration 

 through a Berkefeld filter, and the active tuberculin protein pre- 

 cipitated from the medium at a given isoelectric point by am- 

 monium sulphate. The precipitate is purified by eight successive 

 precipitations. The precipitate obtained in the operation is dis- 

 solved in distilled water and the protein precipitated by ethyl 

 alcohol. Subsequent purification of the protein is accomplished by 

 a series of isoelectric precipitations. 



Mariette and Fenger working in collaboration with Funk, 

 Huntoon and White (1932) have carried out extensive studies of 

 MA-100 proteins olitained from the human, bovine and avian 

 tubercle liacillus and from a culture of the timothy bacillus. In 

 preparing the purified tubercle l)acillus protein they apparently 

 employed a modification of IVLasucci's and McAlpine's method, 

 since they say tluit precipitation at a given isoelectric point was ac- 

 complished by means of glacial acetic acid. They recommend 

 the use of MA-100 tul)ercle bacillus (human) protein in diagnostic 

 work. The results of their studies and also those of Funk and 

 Huntoon (1930) are discussed later in this chapter. 



Relationship of Molecular Weight to Sensitizing Property, 

 — In 1933 Seibert reported upon the relationship between the sen- 

 sitizing properties of tuberculin and its molecular weight. Numer- 

 ous .studies had indicated that while OT, TPA, TPT, and SOTT or 

 PPD are all capable of eliciting specific allergic reactions in tuber- 

 culous animals, they differ markedly in the degree of sensitization 

 to tuberculin produced by repeated injections of the respective 

 products into the animal body. Since Svedberg had emphasized 

 the fact that in dealing with purified proteins the final molecular 

 size of the latter will depend upon the method of isolation, it 

 occurred to Seibert that differences in the molecular weight of 

 OT, TPA and TPT might result from the methods used in their 

 preparation and that some correlation between the molecular weight 

 and sensitizing property might exist. Her experimental investi- 

 gation led her to believe until recently (1941) that such is the 

 ease. 



