LOCAL IMMUNITY 



surface, not concentrated on the points where lymphoid 

 follicles occur, so that we must regard the focal rather than 

 diffuse distribution of the lymphoid tissue as having one or 

 both of two reasons. In the first place they must represent 

 a focal distribution of a mechanism which can distribute the 

 immediate protective agents uniformly over the whole 

 mucous area concerned. This must be common to any 

 interpretation and a plausible expansion of the idea is that 

 there is continuous seeping of protective substance on to 

 the mucosal surface, where it spreads between the cell surface 

 and the protective film of mucus. This will probably allow 

 the maintenance of a high concentration of antibody or other 

 protective globulins in the region where it will be most 

 effective. The reasons for the focal nature could be (a) that 

 this does the least harm to the physiological functioning of the 

 viscus concerned or (b) that there are immunological func- 

 tions which can only be served when a germinal centre 

 develops, that is, are only possible in a lymphoid follicle or 

 larger accumulation. 



Since the movement of locally produced antibody is to 

 the lumen, it will not necessarily be reflected in a similar 

 antibody level in the blood. Similarly, unless the pathogen 

 (antigen) comes from the lumen, this mechanism cannot be 

 laid down. Parenteral vaccination would therefore not be 

 expected to produce intestinal immunity to anything like 

 the same degree. 



The logical extension of this point of view is to bring into 

 the picture the glands responsible for part of the moistening 

 and lubrication of the surfaces. We have been particularly 

 impressed by the plasma cells in immediate relation to the 

 tracheal glands in influenza — since it would be completely 

 in line with current thought about the nature of immunity 

 to influenza if a large component of the antibody known to 

 be present on the respiratory epithelium were derived from 

 local production as well as, or instead of, from the general 

 circulation. Of even greater interest is the possible role of the 



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