IV. CONTRIBUTIONS TO THE STUDY OF IMMUNITY. 1 



By Dr. von DUNGERN, University of Freiburg, Germany. 



A. New Experiments on the Side-chain Theory. 



THE combining experiments of Ehrlich and Morgenroth 2 showed 

 conclusively that the two components of an immune serum necessary 

 for haemolysis and first demonstrated by Bordet, namely the immune 

 body which withstands heating to 56 C. and the complement (addi- 

 ment) which is present even in normal serum, can under certain cir- 

 cumstances exist in a serum side by side, uncombined. The immune 

 body possessed a strong affinity to the blood-cells to which it spe- 

 cifically belonged, being anchored by these cells at C. and thus 

 separated from the complement, which latter remained in the serum. 

 The complement was abstracted from the serum by the erythrocytes 

 only at higher temperatures provided the immune body was present 

 at the same time. When the latter was absent the blood-cells failed 

 to combine with any complement whatever. The complement, 

 therefore, because of its lack of affinity, was unable to act on the 

 blood-cells, and likewise the mere anchoring of the immune body 

 by the blood-cells, without the presence of the complement, was 

 unable to effect any haemolysis. The most plausible explanation 

 for these facts was this, that solution is effected by the complement, 

 but that this substance first requires the immune body to enable it 

 to lay hold of the blood-cells. 



Bordet 3 has assumed that the immune body, independently of 

 the complement, combines with the substance of the erythrocyte 

 and so changes this that it (the erythrocyte) now combines with 

 the complement. Against this assumption must be urged that 

 as a matter of fact there is a definite relation between immune body 



1 Reprinted from the Miinchener med. Wochensohrift, No. 20, 1900. 



2 See pages 1-23 of this volume. 



3 Annales de 1'Institut Pasteur, 1899, No. 14. 



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