Infectious Disease: Evolving Challenges to Human Health

Acquiring Immunity, Remembering Infections

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When the body is exposed to viruses, bacteria, fungi, or parasites through an infection or vaccination the immune system creates antibodies and immune cells that inactivate or destroy the specific infectious organism. If we encounter the same organism in the future, the immune system “remembers” that previous exposure and can mount a vigorous defense.

We gain specific immunity in several ways. We gain temporary immunity to some diseases by acquiring antibodies directly from our mothers when we are in the womb. Throughout life, we gain specific immunity as we are exposed to new organisms. Infections create memory cells that can protect us from future infection from the same or related organisms. Vaccines stimulate the same process.

INFECTION – The immune system recognizes foreign proteins or complex sugars by their unique shapes. One key to specific immunity lies in the body’s ability to manufacture large numbers of antibodies that match each of these shapes. Antibodies swarm the infecting organisms, attaching themselves to the foreign organisms and blocking the ability of the organism to attach to human cells. Immune system cells use the attached antibodies as handles to grasp the infectious organisms for destruction or removal.

VACCINATION – Vaccines present a pathogenic organism’s proteins or complex sugars to the immune system. A vaccine stimulates the natural immune response, creating antibodies and a memory of the infection without the danger of an actual infection. The memory helps protect us if we are ever exposed to the pathogen in the future.

FUTURE EXPOSURE – If a person is exposed to the same disease in the future, the body already has a memory of the infection and can quickly fight off the infection.

Graph showing antiboty response after vaccination and infection
The green line shows antibody levels in response to an infection and a future reinfection. The red line show antibody levels in response to vaccination and then a future infection. The lines are similar in shape and level.

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