TOXINS OF CL. WELGHII 



867 



brief outline of the properties and relationships of the CI. welchii toxins. For a full dis- 

 cussion the reader is referred to the exhaustive review of Oakley (1943) from which, with 

 certain modifications, we reproduce Table 54, showing the toxins pi'esent in the different 

 filtrates, and Table 55, showing the projjcrties of the toxins. 



TABLE 54 



Giving the Distribution of Toxic Components in Culture Filtrates of CI. welchii 



(Oakley 1943) 



It will be seen that the a toxin predominates in Type A, ^ and e in Type B, fi and (5 in 

 Type C and s in Type D filtrates. The distinctions, botli qualitative and quantitative, 

 between the types are not absolute. Mason (1935), for instance, records the loss of ability 

 to produce e-toxin in Type B strains, Borthwick (1937) a similar loss in Type D strains, 

 and Taylor (1940) a loss of ^-toxigenicity in a Type B strain. The properties of the 

 toxins are summarized in Table 55. 



TABLE 55 

 Giving the Properties of the Toxins of CI. welchii (Oakley 1943) 



The a-toxin is a thermostable substance, lethal for mice, guinea-pigs, rabbits, pigeons 

 and sheep, and when given intradermally, produces a necrotic lesion. It is haemolytic 

 for the red cells of most laboratory animals excepting the horse and the goat, and is a 

 powerful leeithinase. The leeithinase activity of a -toxin is of great interest, since it is 

 the first known instance of an exotoxin dependent upon a demonstrable enzyme for its 

 activity. Its discovery dates from the demonstration by Nagler (1939) that toxic filtrates 

 of all four types of CI. welchii produced an opalescence in human sera, and that the reaction 

 was specifically inhibited by antisera to Type A filtrates (see also Seiffert 1939). The 

 reactivity ran parallel to the toxin content of filtrates. Macfarlane, Oakley and Anderson 

 (1941) demonstrated a similar action of a-toxm on extract of egg yolk, and suggested 

 that both phenomena were due to an enzymic spUtting of Hpo-protein complexes in 

 serum and egg-yolk respectively ; and that haemolysis by a-toxin might also be due to 

 its action on Upo-proteins in the red cell envelope. The identity of a-toxin and leeithinase 

 was further estabhshed by Macfarlane and Knight (1941), who demonstrated a quantitative 

 splitting of lecithin by a-toxin, into phosphocholine and a glyceride, and the necessity 

 for Ca or Mg ions in the reaction. The leeithinase activity of a filtrate may be used as 



