On the specific acquired resistance of red blood cells

It is a well known fact that the serum plays a preponderating rôle in the immune reactions of animals. On the other hand, it has been amply shown that the immune characters of the serum may be in no proportion to the immunity of the organism as a whole. There must therefore be an additional factor, hypothetically designated by Behring as cytogenetic immunity. Of this type of immunity there is the following experimental evidence. In 1898, Kossel stated that if an animal were injected with eel serum, its washed red cells manifested resistance to the hemolytic action of the latter in vitro; a fact confirmed by Camus and Gley, and by Tshistovitch. In 1908, it was shown by Morawitz and Pratt that in animals injected with phenylhydrazin, the red cells became resistant to all hemolytic agents. This they showed to be not an immune reaction, but the direct result of the chemical action of the drug on the red cells.