MECHANISM OF ANTIBODY FORMATION 113 



out affecting the degree of enzyme activity and immunological speci- 

 ficity (Northrop, et ah 1948). It would be interesting to know how far 

 one can reduce the molecular size of the smallest of the three chymo- 

 trypsins without affecting its serological and enzymatic properties. 



c. Virus-Host Relationship. The experimental demonstration of the 

 independence of the biophysical and serological specificities of virus 

 preparations derived from different species of hosts may, at present, 

 for technical reasons, be difficult to achieve, particularly with animal 

 viruses of greater complexity and particle size which have not lent 

 themselves to purification, for example, by crystallization. 



The failure to separate the host components from such virus prepara- 

 tions may easily give rise to assumptions that these viruses carry the 

 specificity of tissues from which they are derived. It has been reported 

 (Knight, 1946), for example, that the virus of influenza contains a 

 specific normal component which is characteristic of each individual 

 host from which the virus is obtained. However, this component ex- 

 hibits a serological specificity distinct from that of the virus. On the 

 other hand, similar studies with plant viruses which are simpler in 

 composition and are obtainable in crystalline form have shown the 

 biophysical and serological individuality of the viruses irrespective 

 of the plant hosts in which they are multiplied (Bawden and Pirie, 

 1944, 1946; Gaw and Stanley, 1947; Malkiel, 1947). It has been 

 found that the purified preparations of tomato bushy stunt virus de- 

 rived from the leaf sap and the fibrous residues of infected tomato 

 plants did not differ in any significant manner. Purified tobacco mosaic 

 virus and the rib-grass strain of tobacco mosaic virus, in these respects, 

 showed identical properties. Malkiel (1947) reported that there was 

 no serological difference found for either tobacco mosaic virus or rib- 

 grass virus when each was isolated from widely separated plant species. 

 Immunochemical studies failed to indicate the presence of any normal 

 host protein as a component of any of the virus preparations. These 

 findings do not offer any support to the assumption that the viruses 

 are autocatalytically derived from a normal proteinogen possessing the 

 species characteristics of the host in which the virus multiplies. 



And there are, at present, no data to indicate that normal host pro- 

 teins or the viruses derived from the host can be modified chemically 

 or otherwise, to show any serological interrelationship suggestive of 

 the autocatalytic origin of viruses from the host proteins. 



