Humoral theory of immunity

“The most telling blow to the cellular theory of immunity came in 1890 with the discovery by von Behring and Kitasato that immunity to diphtheria and tetanus is due to antibodies against the exotoxins of these bacteria. When, shortly thereafter it was demonstrated that passive transfer of immune serum would protect the naïve recipient from diphtheria, with no obvious intercession by any cellular elements, the humoralists felt that they had been vindicated, and Koch felt free to proclaim the demise of the phagocytic theory at a congress in 1891. The discovery of antibodies against these exotoxins, and even against toxins of nonbacterial origin such as ricin and abrin, supported the earlier view that most infectious diseases were toxic in nature; thus, it could be claimed that protection was due in large part to humoral antitoxic antibodies” (Silverstein, 49-50).