Immune System

By: Francisco Colina-Salas


Protect against disease or other potentially damaging foreign bodies.

Terms to Know

Pathogen: a bacterium, virus, or other microorganism that can cause disease.

Active Immunity: the immunity that results from the production of antibodies by the immune system in response to the presence of an antigen.

Passive Immunity: the short-term immunity that results from the introduction of antibodies from another person or animal.

Antigen: a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.

Antibody: a blood protein produced in response to and counteracting a specific antigen.

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Why are antibiotics are effective against bacteria but not against viruses?

Antibiotics are produced by microorganisms to kill or control the growth of other microorganisms by blocking specific metabolic pathways within the cell. Since bacteria are so different to human cells, antibiotics can be taken by humans to kill bacteria without harming the human cells. Viruses on the other hand are different as they do not carry out many metabolic processes themselves. Instead they rely on a host cell (a human cell) to carry out these processes for them. Therefore viruses cannot be treated with antibiotics as it is impossible to harm the virus without harming the human cells.


  1. A chronic immune system disease caused by HIV (human immunodeficiency virus)

  2. Pain: in the abdomen, can occur while swallowing. Cough: can be dry. Gastrointestinal: persistent diarrhea, watery diarrhea, vomiting, or diarrhea. Throat: soreness or difficulty swallowing. Mouth: white tongue or ulcers. Groin: sores or swelling. Whole body: loss of appetite, fever, night sweats, malaise, fatigue, sweating, or nausea. Also common: opportunistic infection, swollen lymph nodes, oral thrush, red blotches, skin rash, unintentional weight loss, headache, or pneumonia

  3. 200K to 3M US cases per year

  4. Antivirals