734 HETEROPHILE ANTIGENS AND ANTIBODIES 



blood corpuscles of a given species it does not, as a rule, occur in any other tissue and 

 vice versa, but the domestic fowl is an exception to this rule, the antigen occurring 

 both in the blood and other tissues. The antigen is not equally distributed in the dif- 

 ferent organs and tissues of "heterophile" animals; the kidney tissue of the horse and 

 guinea pig seems to be particularly rich in heterophile antigen. It has even been found 

 in the urine of certain species — e.g., horse and guinea pig. 



It is seen that heterophile antigen is widely and apparently quite promiscuously 

 distributed in nature. It is found in the chicken but not in the pigeon; in mice but 

 not in rats; in certain paratyphoid bacilli, but not in typhoid bacilli; in certain fish 

 (gills only), but not in many others. 



PHYSICAL AND CHEMICAL PROPERTIES OF HETEROPHILE ANTIGEN 



As already stated, heterophile antigen is very resistant to heat. Sheep corpuscles, 

 e.g., can be kept in boiling water for hours with little or no reduction of their content 

 of this antigen. The same is true of emulsions of the kidney tissues of the guinea pig, 

 horse, etc. Even heating in an autoclave at 120° C. for an hour does not destroy the 

 power of these antigens either to produce or to combine with antibodies. This prop- 

 erty alone puts heterophile antigens in a class to themselves, for ordinary antigenic 

 substances are easily injured by heat. 



Heterophile antigen seems to be very firmly held by the formed elements of the 

 tissues containing it, since juices obtained from such tissues by mechanical means 

 contain only a very little of it. Organ plasma prepared according to Pohl's method 

 contains the antigen. Treatment of this plasma with a weak solution of acetic acid 

 causes the antigen to be precipitated. Pohl's acetic acid body obtained from the organ 

 plasma is believed to be identical with heterophile antigen. 



Chemically,' heterophile antigen appears to consist of a complex of two fractions. 

 The entire complex is necessary for the stimulation of antibody production in animals, 

 but only one fraction is active in test tube reactions. The latter fraction can be ex- 

 tracted from tissues with alcohol. It is insoluble in acetone but soluble in petroleum 

 ether. It is believed to belong to the lecithin group of lipoids. This fraction is not 

 capable of stimulating the production of antibodies, but it reacts specifically with 

 heterophile antibodies in vitro. 



The fraction remaining in the tissue residue after extraction with alcohol is be- 

 lieved to be a protein. This fraction is inactive both in vivo and in vitro. If the two 

 fractions are mixed and injected into animals, no antibodies are produced. Land- 

 steiner and Simms^ claim to have restored the antigenic power of heterophile lipoids 

 by treating them with foreign protein, particularly with serum, but the antibody 

 response of the animals treated with these reconstituted heterophile antigens was not 

 very striking. 



It seems, then, that one is justified in concluding that the thermostable antigenic 

 substance found in the blood corpuscles of sheep and goats, and in the organs and tis- 

 sues of various other animals, is a protein-lipoid complex which can be disrupted by 

 treatment with alcohol. The whole complex is necessary for the stimulation of the pro- 



' Meyer, Kurt: ibid., 122, 225. 1921; Taniguchi, T.: J. Path. &■ Bad., 23, 364. 1920. 

 ' Landsteiner, K., and Simms, S.: J. Exper. Med., 38, 127. 1923. 



