CHAPTER LII 



ANTIGENIC PROPERTIES OF THE BACTERIAL CELL 

 AND ANTIBODY REACTIONS 



HANS ZINSSER and J. HOWARD MUELLER 

 Harvard University Medical School 



I 



The processes of immunity by which the animal body resists invasion and injury 

 by bacteria are merely specific instances of the operation of general biological laws 

 applicable to a field far wider than that of infectious disease. The elaborately ad- 

 justed and complicated mechanism of which we speak as "immunity" is the con- 

 sequence of a physiological response which, in its broad biological significance, may be 

 stated as follows: 



Under conditions of normal metabolism, the tissue cells come in contact with ex- 

 traneous substances only as the products of digestion or as adventitious, diffusible 

 materials that, as a rule, are readily disposed of. It is almost inevitable, however, 

 that, in the course of life, complex substances — carbohydrate, lipoidal or protein — • 

 may gain entrance without preliminary digestive transformation to assimilable form. 

 As far as the lipoids and carbohydrates' are concerned, no consequences that fall into 

 the field of the immunologist develop, and it is more than likely that these materials 

 can either be taken care of or eliminated without giving rise to lasting changes in cell 

 reaction. With complex nitrogenous materials (proteins or closely related substances)^ 

 this is not the case. Here, contact with the tissue cells sets in motion an emergency 

 mechanism which reveals itself by a specifically changed reaction capacity of the 

 tissue cells. In many cases — those in regard to which we have the most extensive in- 

 formation — this changed reaction capacity is characterized, among other things, by 

 the appearance in the blood stream of specific reaction bodies to which the name "anti- 

 bodies" has been applied. In other cases, however — notably with foreign substances 

 responsible for the various allergies — profound specific changes in cell reaction may 

 be developed in every fundamental attribute analogous to the former, except that no 

 determinable circulating antibodies can be detected. Thus, while it is of course im- 

 portant to distinguish between foreign materials which call forth antibody formation 

 and those which do not, it is necessary to bear in mind that the appearance of these 

 circulating reagents is purely secondary to a specific cell response and, this having 

 taken place, the development of antibodies in the blood may or may not follow — 

 depending upon the chemical and physical peculiarities of the inciting antigen.^ Thus, 



' Except in protein combination as described below. 



^ We cannot, in a definition of this kind, cover the entire Geld by qualifying it for tlie relatively 

 simple substances concerned in drug idiosyncrasy. This would involve prolonged theoretical discus- 

 sion not pertinent to our present purposes. 



' It does not seem pertinent to the purposes of this paper to enter into a complicated discussion 

 on the nature of the circulating antibodies. In former communications we have advanced arguments 



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