QUALITATIVE IMMUNE RESPONSES 



important question of whether sensitive cells are repre- 

 sentatives of immunologically modified clones or have, in 

 part at least, been altered by some non-genetic process. 

 Much interest has therefore been devoted to the nature of 

 the cells associated with the response. 



It is easy to show that cells from the spleen of a tuberculous 

 guinea-pig grown in tissue culture are sensitive to a severely 

 damaging effect when tested with dilute tuberculin, normal 

 cells being unaffected. This reaction is confined to mesen- 

 chymal cells, not being shown by corneal cells or a variety of 

 other epithelial cells obtained from tuberculous animals 

 (May and Weiser, 1956). The genesis of this type of reactivity 

 seems to be associated with a special type of cellular response 

 best initiated by the simultaneous presence of waxy materials 

 of the type found in the tubercle bacillus. Raffel and Forney 

 (1948), for instance, showed that typical 'contact dermatitis' 

 sensitization could be produced in guinea-pigs by intra- 

 peritoneal injection of picryl chloride plus purified wax from 

 tubercle bacilli. In the absence of the wax, sensitization can 

 only be produced by direct contact of the chemical with the skin. 



Homograft immunity is not associated with circulating 

 antibody. The most elegant demonstration of this is by 

 Algire's method of applying a foreign graft that is separated 

 from the immune host by a membrane which allows passage 

 of protein molecules but not of cells. Under these circum- 

 stances, the graft remains undamaged. 



All three types of reactivity can be transferred to a normal 

 animal by suspensions of mesenchymal cells in which 

 lymphocytes seem to be the most significant element. In 

 studies with picryl chloride, Battisto and Chase (1955) 

 found that they could render guinea-pigs insusceptible to 

 sensitization by the normal procedure if the allergenic 

 chemical was fed to the animals for a preceding period. This 

 failure to react, however, did not prevent the passive transfer 

 of hypersensitivity to the non-reactive animal by cells from 

 one that had produced typical active hypersensitivity. Also 



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