Evolution of Immunology: From Pasteur to Modern Vaccines
Understanding the Immune System’s Organization
Scientific research over many years has led to our understanding of the immune system’s organization and function (Supplementary reference text).
Louis Pasteur (1822 – 1895)
The 17th and 18th-century disease concept suggested that diseases were inherent from birth. This changed after 1870 with Louis Pasteur, Robert Koch, and others who identified infectious agents. Pasteur showed that acquired immunity could be induced by immunization with attenuated pathogens. In 1880, Pasteur and Emile Roux discovered variations in pathogen strains, leading to research on preventive immunization, inspired by Edward Jenner’s smallpox vaccination.
Emile Roux and Alexandre Yersin (1888)
They isolated a soluble toxin from diphtheria, showing that symptoms were caused by an exotoxin. Von Behring and Kitasato later found that immunized animals produced substances (Antikörper or antibodies) that neutralized toxins. This led to serotherapy, earning von Behring the 1901 Nobel Prize in Medicine.
Paul Ehrlich (1897)
Ehrlich proposed that antibodies matched antigen structures, functioning as cell surface receptors. This theory influenced immunology for decades, earning him the 1908 Nobel Prize in Medicine.
Jules Bordet (1899)
Bordet discovered that antibodies with complement could destroy erythrocytes, leading to new diagnostic methods. This earned him the 1919 Nobel Prize in Medicine. Karl Landsteiner used these findings to develop the ABO blood group system.
Cellular vs. Humoral Immunity
Early immunology saw debates between cellular and humoral immunity theories. Paul Ehrlich championed humoral immunity, while Ilya Metchnikoff proposed the cellular theory, discovering phagocytic leukocytes. Both received the 1908 Nobel Prize in Medicine, recognizing both theories’ importance.
The Immune Response: An Internal Defense System
Animals have internal defenses against pathogens. The immune system distinguishes self from non-self, recognizing foreign macromolecules. The term immune means safe or secure. Immunology studies these defense mechanisms.
There are two main types of immune responses:
- Nonspecific (innate): General protection, like skin barriers and phagocytosis.
- Specific (adaptive): Targeted responses to specific antigens, including antibody production and immune memory.
Invertebrate vs. Vertebrate Defense Mechanisms
Invertebrates have nonspecific defenses like phagocytosis and some specificity. Vertebrates have complex immune responses with lymphocytes and a lymphatic system.
Activity 6
Create a two-way table comparing invertebrate/vertebrate and specific/nonspecific immunity.
The immune system provides rapid, specific protection against pathogens. Its importance is evident in immunodeficiency cases. Immunity can be manipulated through vaccination, pioneered by Edward Jenner.
Infectious Disease Statistics in Chile
Figure 16 shows the impact of vaccines on common infectious diseases.
Components of Innate Immunity
Innate immunity includes physical barriers (skin), chemical barriers (sweat, sebum), phagocytic cells, and plasma proteins. Lysozyme in sweat and tears degrades bacterial cell walls.