ii8 Immunity 



An analysis of tliis theory shows complete natural immunity 

 to depend upon the absence of haptophore groups (receptors) by 

 which the toxins can be united to the cells. Extreme sensitivity 

 or susceptibility probably depends upon the adapted haptophores 

 being present or at least most numerous upon the cells of highly 

 vital organs; comparative insensitivity or insusceptibility upon 

 the fact that the greater number of haptophore groups are attached 

 to comparatively unimportant cells whose combining affinities 

 have to be satisfied before combination with more vital cells can 

 be accomplished. In some cases natural immunity is increased by 

 the presence of free haptophore groups (antitoxin) in the blood. 



Acquired immunity against toxins depends 

 upon the regeneration of the cellular hapto- 

 phores or receptors which, being liberated 

 into the body juices, fix the haptophores of 

 the toxin molecules before they are able to 

 reach the cells themselves. Antitoxins and 

 other anti-bodies, including the lysins, consist 

 of liberated cellular haptophores or receptors, 

 the former having a single combining affinity, 

 the latter a double combining affinity, by 

 which they unite, on the one hand, with the 

 Fig. 26.-Cellwithre- ^ ^ ^^ dissolved, on the other with the 

 ceptors of the second ..... i i- i j 



order (a) by which the complement by which it IS to be dissolved, 

 cells fix useful molecules, Antibodies having this double combining 

 hin'd'cS'and Vmog^: affinity have been called "amboceptors" by 

 molecules (c) on the other Ehrlich. They are variously known in dif- 



hand, and make use of the fgrent writings as "immune bodies," ambo- 

 one substance through , , , ., ., . ^ . , , 



the action of the other. ceptors, substance sensibiksatrice, desmon, and 



fixateur. The "complement" or "addi- 

 ment" of Ehrlich is also called alexin and cytase. Ehrlich con- 

 ceives every amboceptor and every complement to be specific, but 

 Bordet and others, while admitting that the amboceptor is specific, 

 hold that there is but one complement or cytase. 



It has already been said that MetschnikofE's primitive con- 

 ception of the body being defended against infection through the 

 phagocytic incorporation and digestion of the microparasites, has 

 had to be modified to conform to the increasing information upon 

 the immunity reactions. He has persistently clung to the idea that 

 the phagocytes are the essential factors, but has changed the con- 

 ception of "phagocytosis" to make it applicable to the new require- 

 ments. He now teaches that when invasive-micro-organisms enter 

 the body, chemotactic influences determine that they shall be met 

 by phagocytes. If the invading micro-organisms are too powerful 

 and the phagocytes are killed, phagolysis or dissolution of the phago- 

 cytes liberates their enzymes into the blood. These liberated 

 enzymes still act deleteriously upon the invaders, tending to ag- 



