[The doctrine of immunity in the light of Robert Koch's concepts].

Robert Koch's epochal discovery of the tubercle bacilli provided the first complete evidence for the specific nature of the causative agents of the most important human infectious disease. It was on this basis that Koch developed his ideas about the doctrine of immunity. The high specificity of "Koch's basic experiment" became the cornerstone of the specific early recognition and prophylaxis of tuberculosis and provided a pattern of specific immune diagnostics in general. Basing on the antitoxin experiments of Behring and Ehrlich against diphtheria and tetanus, Koch presumed humoral immune mechanisms to exist also for tuberculosis. These investigations were abandoned after long-lasting efforts. The concept of Robert Koch and his school about the specific humoral immunity of infectious diseases was dominating immunological research for half a century until the elucidation of the cellular nature of the tuberculin reaction became a general asset of modern immunology. Only thereafter this discipline gave full swing from the immunochemical to the immunobiological approach. Robert Koch's merits as a physician and as an investigator reside in his strictly causal-analytical way of thinking and working which was adopted also in the search for the causes of cancer. In studying the immunological virus-host relationship one arrives from the "whence" of the disease at the "why" of its pathological form. This may be conceived of as a conceptual model for problems concerning the biological evolution and differentiation in modern pathology.