THE COURSE OF INFECTIOUS DISEASE 



Cheatham that plasma cells are very inconspicuous in the 

 lung, which would be in line with a general inability to respond 

 effectively to an immunological demand. 



Recent work suggests strongly that canine distemper is 

 due to a virus closely related to measles (Carlstrom, 1956), 

 and it is of much interest that mink, which are highly sus- 

 ceptible to the disease, may die with a giant-cell pneumonia 

 biologically almost identical with that of children with post- 

 measles giant-cell pneumonia (Pinkerton, Smiley and 

 Anderson, 1945). 



3. Streptococcal infections 



One of the most important unsolved problems in medicine 

 is the pathogenesis of rheumatic fever. The relation to 

 pharyngeal infection with haemolytic streptococci is un- 

 doubted and there is a firm body of opinion that an im- 

 munological process is involved. The difficulty both here 

 and for the related problem of acute glomerulo-nephritis 

 is to define the nature of the hypothetical immunological 

 process. 



It has already been suggested that the answer may be 

 found in the relationship of the streptococcus to the masses 

 of mesenchymal cells in the tonsils and other accumulations 

 of lymphoid tissue in the pharyngeal region. We have fre- 

 quently pointed out that any clonal selection theory must 

 accept the certainty that forbidden clones will constantly be 

 arising and that in some way the normal body must inhibit 

 or destroy such cells. We have constantly referred to the 

 homeostatic mechanism needed to accomplish this. The 

 existence of such a mechanism will have almost as a corol- 

 lary the possibility of its distortion or loss under some 

 circumstances. 



It is not intrinsically unreasonable therefore to wonder 

 whether the sub-acute infection of large regions of lymphoid 

 tissue by streptococci might not sometimes distort the homeo- 

 static control. As a working hypothesis to be studied for its 



156 



