PRIMARY AND SECONDARY RESPONSE 



cells. The possibility of some of this secondary antigen being 

 liberated, say from macrophages in which it had been partly 

 disintegrated, must be borne in mind. When, however, we 

 have a situation where both first and second inoculum is 

 inadequate to produce antibody as a primary stimulus, yet 

 a high titre response is given to the second, the separation of 

 the tooling-up from the antibody-producing process is almost 

 the only way to account for the observations. 



Fig. 5. A comparison of primary and secondary responses in mice to 

 immunization with a bacteriophage (G 16). Ordinates show the activity 

 of serum expressed as K. The primary dose in number of infective particles 

 inoculated is shown above. After the primary response had been 

 titrated all mice were given a uniform dose of 10' phage particles. 



3. The lack of immunological reactivity to body constituents 



It is axiomatic that no immunological reaction takes place 

 against the normal constituents of the body; no other 

 situation is conceivable in health, and the variety of serious 

 diseases which arise when this rule is transgressed merely 

 underlines its importance. As is the case in many biological 

 fields, a situation which functions smoothly and incon- 



33 



