A Brief History of Microbiology

Before 1400, variolation was a common immunology practice. This involves using scabs from smallpox to inject and treat/prevent smallpox from occurring in healthy individuals. This technique was brought to Europe by the 1700s by Lady Montague who came across it during her travels of the world and was greatly promoted during the Revolutionary War. Variolation protected some individuals, however others were infected instead. In 1798, an English doctor named Edward Jenner noticed that people who worked with cows rarely contracted smallpox; sometimes they did get cowpox, though, a disease that wasn’t as severe as smallpox. Jenner then used cowpox scabs to make a successful smallpox vaccine. (Smallpox is the variola virus, cowpox is the vaccinia virus.) The last recorded case of smallpox was in 1977 in Somalia.

In the 1880s, Louis Pasteur coined the term “vaccine” which he worked on mostly for agricultural purposes. Pasteur was the first to develop a vaccine for rabies.

In 1901, Emil von Behring won the Nobel Prize for his work with antiserum. He found several functions of antiserum:

• Transfers immunity
• Neutralizes toxins (by “anti-toxins” in the blood)
• Precipitates bacteria (“precipitins” produce clumps)
• Agglutinates red blood cells (by “agglutinins”)
• Lyses red blood cells (by “hemolysins”)
  

Everything found by von Behring about antiserum are actually parts of antibodies – proteins found in γ-globulin fragments.

Immunoglobulin = antibody

Humoral antibodies, found in fluids, were the first antibodies to be discovered.

Around 1893, scientists began looking at immunological properties of cells, but getting conflicting results. Elie Metchnikov won the Nobel Prize in 1908 with his discovery of phagocytes. Metchnikov stressed the importance of cells and cell-mediated immunity.

Animals can respond to a variety of antigens. Two theories as to how this is possible:
1. Instructional Theory – The body has receptors for different compounds, which mold and adapt to the compound. The antigen modifies the receptor. (Incorrect)
2. Selection Theory – The body has receptors even before exposure. The antigen selects for the correct receptor. (Correct)
Antibodies can respond to viruses, bacteria, fungi, and parasites.

Two types of immunity:
1. Innate immunity – Not specific to a particular pathogen, provides immediate response against infection. Recognizes unusual classes of molecules and tries to combat them before they can infect host cells. Includes barriers such as the skin, mucosal membranes, and stomach acid.
2. Adaptive immunity – Specific recognition to a particular pathogen or threat. Also has the ability to “remember” certain antigens to more effectively eliminate them at a later time.