CHAPTER XVII 

 BIOLOGICAL AND ANTIGENIC SPECIFICITY 



Immunological Specificity, — In the previous pages attention 

 has been directed to the phenomenon of immunological specificity 

 wherein a specific antigen not only stimulates the physiological 

 ]>roduction of specific antibodies but reacts only with the anti- 

 bodies thus formed. Landsteiner (1936, p. 5) points out that 

 specificity is not an entirely absolute quality but that there is 

 always some overlapping. Loeb (1916), Wells (1929), Zinsser, 

 Enders and Fothergill (1939) and others have called attention to 

 the general biological significance of specificity and have reviewed 

 the literature and offered experimental evidence pointing to a 

 chemical basis for all specificity. 



Biological Specificity. — Experience in animal breeding and in 

 cross fertilization has shown that success is attained only when 

 eggs and spermatozoa of the same or very closely related species 

 are used. 



Specificity and Incompatibility of Species.— In discussing the 

 incompatibility of species not closely related, Loeb mentions the 

 rigid specificity requirements for successful skin grafting or or- 

 gan transplantation. It is the experience of every plastic surgeon 

 that the best results are obtained when the skin from the patient's 

 own body is used or from members of the family who belong to the 

 same blood group. In any event skin from a different species 

 cannot be used for a successful graft. The same applies to 

 organ transplantation. 



Specificity^ and Fertilization. — Loeb also calls attention to the 

 specificity requirements in the fertilization of an egg by a sperm. 

 In this process many phenomena analogous to those observed in 

 immunity are encountered. The first of these is positive chemo- 

 taxis. Pfeiffer showed that fern spermatozoa are deviated in 

 their course when they a]iproach an archegonium containing an 

 egg, and that the attraction is sufficient to cause the sperm to 

 enter the archegonium and permit contact and ultimate fertiliza- 

 tion of the egg. Loeb says that it is a very common experience 



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