The immune system protects the body against external harmful invaders, such as viruses, bacteria, fungi, and so on. The immune system consists of various physical barriers (e.g. membranes), the white blood cells (leukocytes; T-cells and B-cells), and so on. Immune response symptoms include inflammation and infection symptoms. Symptoms of excessive immune response include allergic reaction, hives (urticarial), asthma attack, anaphylaxis, and so on. Immune system disorders include allergies, asthma, hypersensitivity syndromes, autoimmune diseases, and immune deficiency disorders.
• • •
The immune system is a network of cells, tissues, and organs that work together to protect the body from infection. Although scientists have learned much about the immune system, they continue to study how the body targets invading microbes, infected cells, and tumors while ignoring healthy tissues. The combination of new technology and expanded genetic information promises to reveal more about how the body protects itself from disease. In turn, scientists can use this information to develop new strategies for the prevention and treatment of infectious and immune-mediated diseases.
Source: NIAID (NIH)1
• • •
Overview of the Immune System
The overall function of the immune system is to prevent or limit infection. An example of this principle is found in immune-compromised people, including those with genetic immune disorders, immune-debilitating infections like HIV, and even pregnant women, who are susceptible to a range of microbes that typically do not cause infection in healthy individuals.
The immune system can distinguish between normal, healthy cells and unhealthy cells by recognizing a variety of "danger" cues called danger-associated molecular patterns (DAMPs). Cells may be unhealthy because of infection or because of cellular damage caused by non-infectious agents like sunburn or cancer. Infectious microbes such as viruses and bacteria release another set of signals recognized by the immune system called pathogen-associated molecular patterns (PAMPs).
When the immune system first recognizes these signals, it responds to address the problem. If an immune response cannot be activated when there is sufficient need, problems arise, like infection. On the other hand, when an immune response is activated without a real threat or is not turned off once the danger passes, different problems arise, such as allergic reactions and autoimmune disease.
The immune system is complex and pervasive. There are numerous cell types that either circulate throughout the body or reside in a particular tissue. Each cell type plays a unique role, with different ways of recognizing problems, communicating with other cells, and performing their functions. By understanding all the details behind this network, researchers may optimize immune responses to confront specific issues, ranging from infections to cancer.
Source: NIAID (NIH)2
Introduction: Immune system
The Immune System
Your immune system is the network of cells and tissues throughout your body that work together to defend you from invasion and infection. You can think of it as having two parts: the acquired and the innate immune systems.
The acquired (or adaptive) immune system develops as a person grows. It “remembers” invaders so that it can fight them if they come back. When the immune system is working properly, foreign invaders provoke the body to activate immune cells against the invaders and to produce proteins called antibodies that attach to the invaders so that they can be recognized and destroyed. The more primitive innate (or inborn) immune system activates white blood cells to destroy invaders, without using antibodies.
Source: NIAMS (NIH)3
Introduction: Immune system
The Immune System
When your body is attacked—perhaps by a virus or other germs—your immune system defends you. It “sees” and kills the germs that might hurt you.
But when the system doesn’t work right, this process can cause harm. Immune cells can mistake your body’s own cells as invaders and attack them. This "friendly fire" can affect almost any part of the body. It can sometimes affect many parts of the body at once. This is called “autoimmunity” (meaning “self-immunity”).
The part of the immune system that orchestrates all of this develops as a person grows and is known as the acquired immune system. It “remembers” foreign antigens, or proteins, so that it can fight them if they come back. It employs white blood cells called lymphocytes.
Source: NIAMS (NIH)4
• • •
Immune System: The body's defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components.5
• • •
Immune system adverse event: An adverse event that occurs in immune system.6
Read about these related anatomy topics:
- White Blood Cells
- T Cells
- B Cells
- Immune response
- Innate immune system
- Acquired immune system
Read about these related symptoms:
- Hypersensitivity: Hypersensitivity can refer to allergies or a sensitivity to some other substance or stimulant. A person who is hypersensitive to a particular allergen has an allergy to that substance (e
... More on Hypersensitivity »
Disease and Condition Articles
Read about these related conditions and diseases:
- Viruses: Viruses are capsules with genetic material inside. They are very tiny, much smaller than bacteria. Viruses cause familiar infectious diseases such as the common cold, flu and warts. They also7
... More on Viruses »
- Bacterial Infections: Bacteria are tiny single-celled microbes that can infect the body. Some bacterial infections can be quite dangerous and worsen quickly, although they are not always so. Common types of
... More on Bacterial Infections »
- Fungal Infections: Fungal infections are caused by small organisms called fungi (plural) or fungus (singular). They often infect the skin or other external membranes or regions, but can sometimes also infect the
... More on Fungal Infections »
- Inflammation: Inflammation. Swelling of a tissue. It is part of the body’s response to tissue injury, irritation or damage. It is the body’s attempt at self-protection, and this8
... More on Inflammation »
- Allergies: Allergies occur when the immune system responds to a substance. Common examples include dust allergies, pollen allergies (causing hay fever and respiratory allergies) and food allergies. But there are many
... More on Allergies »
Related Symptom Topics
Read more about these related symptoms:More »
Related Disease and Condition Topics
Read about these diseases and medical conditions related to Immune system:More »
• • •
- Source: NIAID (NIH): niaid.nih.gov/ topics/ immunesystem/ Pages/ default.aspx
- Source: NIAID (NIH): niaid.nih.gov/ topics/ immuneSystem/ Pages/ overview.aspx
- Source: NIAMS (NIH): niams.nih.gov/ Health_Info/ Autoimmune/ default.asp
- Source: NIAMS (NIH): niams.nih.gov/ Health_Info/ Autoinflammatory/ default.asp
- Source: MeSH (U.S. National Library of Medicine)
- Source: OAE Ontology
- Source: MedLinePlus (NIH): medlineplus.gov/ viralinfections.html
- Source: RDCRN (NCATS/NIH): rarediseasesnetwork.org/ cms/ cegir/ Learn-More/ Glossary
• • •
Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.