100 BACTERIOPHAGES 



"doughnuts" by Lanni and Lanni (1953); of proflavine lysates 

 of T4, and of T4- and T3-infected bacteria by Barry (1954); 

 and of infected and lysogenic B. megaterium by Miller and Goebel 

 (1954). The antigenicity of ultrafiltrable phage-related ma- 

 terials is discussed below. 



2. Multiplicity of Phage Antigens 



Until a few years ago it was believed, simply because there 

 was no contradictory evidence, that each strain of phage pos- 

 sessed a single kind of antigen. Accordingly, all of the specific 

 eflfects of antiphage serum were interpreted in terms of the reac- 

 tion of a single antibody (neutralizing antibody) with the virus 

 particles. In an extensive study, Lanni and Lanni (1953) 

 (see also Rountree, 1952; De Mars, Luria, Fisher, and Levin- 

 thai, 1953) presented clear evidence for the existence of at least 

 two distinct antigens in phage T2. One of the antigens, which 

 appears to be localized in the phage tail, reacts with neutralizing 

 antibody. The primary measurable eff'ect of this reaction is 

 neutralization of infectivity; under appropriate conditions 

 virus aggregation and complement fixation can also be demon- 

 strated. The second antigen, which appears to be localized in 

 the phage head, participates in specific aggregation and com- 

 plement fixation, but does not react measurably with neutraliz- 

 ing antibody. The two antigens are confined to the surface 

 structures (protein) of the virus ; thus far, the internal contents, 

 liberated by osmotic shock, have given no sign of serological 

 activity (see also Hershey and Chase, 1952; Hershey, 1955). 

 The available evidence indicates that staphylococcal phage 

 3A (Rountree, 1952) and phage T5 (Fodor and Adams, 1955) 

 likewise possess two distinct antigens, only one of which reacts 

 with neutralizing antibody. Evidence bearing on the sero- 

 logical heterogeneity of the phage tail will be discussed in later 

 sections. 



The failure until recently to recognize the antigenic complexity 

 of phage attaches considerable doubt to many of the structural 

 interpretations given to early serological observations. 



