PATHOLOGY OF THE IMMUNE RESPONSE 



All these suggest the production of relatively large amounts 

 of inefficient antibody. 



(e) Haemolytic crises are often seen in association with 

 lymphatic leukaemia, Hodgkin's disease and other 

 reticuloses where one might expect secondary muta- 

 tions of mesenchymal cells already freed (? by somatic 

 mutation) from some of the normal growth controls. 

 The possibility that the occurrence of somatic mutation 

 or some equivalent process can be induced or at least made 

 more frequently visible by virus infection must be kept in 

 mind. The most striking example is the formation of cold 

 agglutinins in virus pneumonia. This is almost constant in 

 the condition due to Eaton's virus and in a small proportion 

 of cases is accentuated to the level of a haemolytic anaemia. 

 The complication is also reported, less commonly, in con- 

 nection with infectious mononucleosis, another presumptive 

 virus disease, which characteristically shows the appearance 

 of non-specific circulating antibodies in high titre. 



In both conditions, and perhaps in other infections not yet 

 recognized, it seems likely that virus infection of lymph nodes 

 or other mesenchymal centres grossly modifies the behaviour 

 of globulin-producing cells. The possibilities to be con- 

 sidered would be either: 



(i) an increased rate of mutation to forbidden patterns, 

 which seems unlikely but not inconceivable when an 

 in-built high mutability is postulated as characteristic 

 of the cell type, or 

 (ii) a functional modification of infected cells rendering 

 them insusceptible to some of the normal controls, 

 including the homeostatic mechanism for the elimina- 

 tion of forbidden clones which we must continually 

 postulate. 

 The strongest evidence in favour of the second is the fact 

 that haemolytic anaemia following either virus pneumonia 

 or infectious mononucleosis tends to show rapid and com- 

 plete clinical and haematological recovery. This in itself 



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