ACQUIRED HAEMOLYTIG ANAEMIAS 



characteristic accumulation of lymphocytes and plasma 

 cells. 



This, taken along with a good deal of other evidence, 

 points to the necessity of postulating a further mode of 

 reaction of the ' sensitized ' mesenchymal cell. When it meets 

 certain types of antigenic determinant, possibly in the form 

 of material which is only slowly liberated from some deposit, 

 the cell gives rise to a proliferative response in epithelioid or 

 metalophil form. 



4. The collagen diseases 



It is generally accepted that there is at least an immunological 

 component in the pathogenesis of the so-called collagen 

 diseases. These are usually listed as: 



(i) Rheumatic fever and acute nephritis. 



(ii) Rheumatoid arthritis. 



(iii) Disseminated lupus erythematosus and related con- 

 ditions such as lupoid hepatitis. 

 (iv) Polymyositis and dermatomyositis. 



(v) Scleroderma. 

 Local accumulations of lymphocytes and plasma cells in, or 

 in the vicinity of, tissues responsible for symptoms are 

 characteristic of all these conditions. Rheumatic fever and 

 acute nephritis are in a rather special category in view of their 

 aetiological relation to streptococcal infection and their pre- 

 dominant attack on the younger age groups. It is probably 

 wise to keep them separate from what might be called (not 

 very happily) the classical collagen diseases ((ii) to (v) above). 

 We may take rheumatoid arthritis as the commonest ex- 

 ample. In this the concentration of gamma globulin is 

 usually higher than normal and two tests of what might be 

 called pseudo-immunological character are usually positive. 

 These are Rose's test (1948) in which sheep cells lightly 

 treated with rabbit anti-sheep red cell serum (amboceptor) 

 are agglutinated by rheumatoid arthritis serum to a much 

 higher level than normal serum, and a capacity to agglutinate 



131 9-2 



