1054 ISOLATION OF SUBSTANCES WITH IMMUNE PROPERTIES 



According to this mechanism of origin, immune substances are colloidal aggre- 

 gates, of relatively large dimension, in which an elementary substance, derived from 

 the host, is adsorbed upon nuclei of a substance derived from the specific antigen. 

 Presumably, the amount of pre-antibody substance associated with one immune unit 

 is approximately the same in any rabbit anti-sheep hemolysin preparation which has 

 not been subjected to denaturing actions. But the amount of antigen substance 

 cemented together by one unit of pre-antibody substance may be extremely variable, 

 depending, roughly, among other things, upon the ratio of the total amount of 

 antigen which has been injected (intravenously) during the immunization procedure 

 to the total amount of immune substance which has been produced. The amount of 

 protein associated with one unit of immune substance may be, therefore, a variable, 

 determined by the conditions of origin. 



The inclusion of specific antigen, in hemolysin, is of a lipoprotein nature related 

 in structure to that of the whole antigen. In the case of antipneumococcus immune 

 substance, the antigen inclusion may well be of a glycoprotein or polysaccharide 

 nature,' accounting for its extraordinary stability toward the denaturing effect of 

 heat.^* 



The character of the pre-antibody substance is not known. Every one of the 

 purified rabbit hemolysin preparations which the writers have tested has elicited 

 anaphylactic sensitization toward rabbit serum when it has been injected into guinea 

 pigs in sufficient quantity. But it cannot be concluded from these tests, in themselves, 

 whether the apparent serum protein content of the preparations tested may be re- 

 garded as an integral part of the immune substances present or as an associated im- 

 purity. The writers are of the opinion that the pre-antibody substance is of the same 

 character as the substances which are the precursors of serum globulin. This opinion 

 is based (i) upon a physico-chemical analysis of a series of purified hemolysin prepara- 

 tions obtained from a corresponding series of sera of greatly divergent character, 

 and (2) upon the fact that the most highly purified preparation obtained has elicited 

 anaphylactic sensitization in a nitrogen concentration approaching the threshold 

 concentration at which whole serum just elicits such sensitization. 



The specific adsorption method of purification, with the special inclusion of the 

 final ether extraction or other device for the destruction of the combining power of 

 the antigen and the removal of the major part of the dispersed antigen substance, has 

 not been applied with much success, as yet, to the purification of sera of the type of 

 diphtheria antitoxin. The difficulty may lie, in this instance, with the raw material, 

 which is a mixture of antitoxin and precipitin. It contains an enormous proportion of 

 antigen substance, and flocculates with the toxin only in restricted proportions which 

 burden the final fractionation with some 90 per cent of non-serum substances. The 

 most nearly pure preparation of antitoxin which the authors have been able to obtain, 

 at this writing, represents a purification of only 10,000 per cent, as compared with the 

 maximum purification of 150,000 per cent obtained with hemolysin.^ 



The non-specific methods of purification, based upon iso-electric fractionations 



■ Heidelberger, M.: Physiol. Rev., 7, 107. 1927. 



* Clowes, G. H. A.: Arch. Path. &* Lab. Med., 2, 456. 1926. J See p. 1050, note 6. 



