The Biology Project: Immunology

Introduction to Immunology

History of Vaccinations


The Chinese are credited with making the observation that deliberately infecting people with mild forms of smallpox could prevent infection with more deadly forms and provide life long protection. Knowledge of the technique, known as variolation, worked its way west to Turkey by the 18th century.

Lady Mary Wortley Montagu, the wife of the British Ambassador to Turkey and who had once survived smallpox, had her children treated and brought the ideas back to Britain, where research began on how to reduce the inoculation's sometimes-awful side effects.

In 1798, the British physician Edward Jenner published his long-term observation that cowpox exposure protected milkmaids from smallpox. To see if this protection could be artificially induced, he exposed a "healthy boy" to cowpox virus from a milkmaid, and then attempted to infect the boy with smallpox. (Obviously, this experimental method is unethical by today's standards.) This method works because cowpox shares antigens with smallpox, but doesn't cause the disease.

Images courtesy of CDC

Fortunately, the vaccine worked. The boy had developed an immunity to smallpox from his exposure to cowpox. The technique of vaccination against smallpox quickly spread through the world. In 1980, the World Health Assembly officially declared "the world and its peoples" free from endemic smallpox. The Immunization Action Coalition is an excellent source of information about childhood, adolescent and adult immunizations and hepatitis B educational materials.
comes from
the Latin word
for cow,

Disease Max. cases (year) 1996 cases
Measles 894,000 (1941) 500
Diphtheria 207,000 (1921) 1
Mumps 152,000 (1968) 600
Since the days of Jenner, scientists have made great progress in developing vaccinations for many diseases. The table to the left shows the effectiveness of three vaccines: measles, diphtheria, and mumps.

Discrimination of self from nonself

The success of the immune system depends on its ability to discriminate between foreign (nonself) and host (self) cells.
Survival requires both the ability to mount a destructive immune response against nonself and the inability to mount a destructive response against self.
-David Huston, Biology of the Immune System, JAMA 278 (22)

When an organism is threatened by microorganisms, viruses, or cancer cells, the immune response acts to provide protection.

Normally, the immune system does not mount a response against self. This lack of an immune response is called tolerance.

In some cases, the immune system does mount an immune response against self. If an error is made, and an immune response is made against self, tolerance to self is lost. This condition is called autoimmunity (from Greek, "self-immunity"). Examples of autoimmune diseases in humans are: asthma, lupus, and arthritis.

The nude mouse cannot mount an immune response

The nude mouse has a defect in its immune system, and can only live if protected from pathogens. The mouse to the right has a transplant of rabbit skin, and can't reject the foreign tissue. Mice with immune deficiencies are very useful in cancer research because human cancer cells can grow into tumors allowing new ways to test cancer therapy.

Important definitions

This problem set will make use of these terms, and give examples of their significance.

The immune system
Cells in our bone marrow, thymus, and the lymphatic system of ducts and nodes, spleen, and blood that function to protect us.
Anything causing an immune response, usually foreign material but may be our own tissues.
Any disease causing micro-organism.
Non-reactivity of the immune system, usually refers to "self" but may include foreign tissue in organ transplants.
A failure of tolerance, the immune system reacts to self.
Molecules released by pathogens and infected tissues to attract cells of the immune system.
Signaling molecules released by one cell to cause a response in another. Signaling is extremely important in our immune response.
Innate immunity
Protection that is always present. Includes phagocytic (cells that eat other cells) macrophages and dendritic cells.
Adaptive immunity
Protection that arises by an immune response, including humoral immunity producing antibodies and cellular immunity.

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Revised: June 17, 2002
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