T AGGLUTININ 



eliminated by contact with the T determinant. In humans 

 the capacity to produce globuHn of the type in question 

 emerges some time after six months of age. Presumably in 

 other animals a similar situation holds. 



In cases of atypical pneumonia the increased titre of 

 T agglutinin is associated with cold agglutinins against 

 human cells. The two antibodies can be shown to be quite 

 distinct by absorption tests. They are presumably produced 

 by two different sets of cells, both of which are stimulated to 

 activity conceivably by a product of the virus responsible or 

 perhaps as a result of actual invasion of the cells by the virus. 



summary: There is no reason to look for other than 

 accidental reasons for the pattern of natural antibodies. Of 

 the wide range of clones in existence at birth some patterns 

 will have recurred more frequently than others and a variety 

 of influences may determine which of these patterns is most 

 frequently set free in the plasma. In addition, there are 

 bound to be globulins with special functions. Properdin 

 may well turn out to be a key substance in the interpretation 

 of antibodies. It was isolated by what are essentially physical 

 methods and its constituent molecules have a wide range of 

 reactivity with various pathogens of at least pseudo-immuno- 

 logical character. It could well represent a significant con- 

 stituent in the population of gamma globulin molecules 

 which is collectively termed an antibody. It is immaterial 

 whether properdin is a special species of globulin evolved 

 by selection ('designed') to act as an emergency general- 

 purpose antibody until more specific antibody populations 

 can be built up or whether it is a sort of pre-antibody secreted 

 in common by cells which on specific stimulation would 

 produce each its own patterned gamma globulin. 



5. The influence of ionizing radiation on immunological responses 



As has already been indicated in discussing tolerance to 

 homografts, it is possible to make a normal animal into one 

 resembling in some respects a neonatal one by whole-body 



99 7-2 



