APPLIED IMMUNOLOGY 



INTRODUCTION 



IMMUNITY AND IMMUNIZATION— NATURAL AND AC- 

 QUIRED IMMUNITY— ACTIVE AND PASSIVE IMMUNIZA- 

 TION—MECHANISM OF THE PRODUCTION OF IMMU- 

 NITY—HISTORY AND DEVELOPMENT OF IMMUNOLOGY 



Definition of Immunity, — Immunity is the resis- 

 tance manifested by man and various animal species to 

 infectious microorganisms or other foreign proteins. 

 It is influenced by numerous factors, as changed en- 

 vironment, physical condition of the animal, species, 

 idiosyncrasies, virulence of the prevalent microbe, etc. 

 Conversely, the absence of this resistance implies 

 susceptibility. Occasionally, hypersusceptibility to 

 certain proteins is observed and to this state of 

 supersensitiveness Richet has applied the term " ana- 

 phylaxis " (see Chapter IV). 



Two kinds of immunity are recognized, natural 

 and acquired. 



Natural Immunity. — The natural or spontaneous 

 resistance of the animal organism to disease is only 



relative, never absolute. The ability of animals to 



1 



