[Intracellular endobiosis as a basic factor in acquired immunity in man (author's transl)].

An attempt is made to explain the significance of intracellular endobiosis for the human acquisition of immunity against cyclic infections diseases. It is pointed out that, taking into account the temporally limited reduplication of an immune-potent cell clone, a species-specific induction of immunity against infections and other diseases is sustained for a sufficiently long period of time only by a microorganism which is still living.