About Immune System
The immune system is a network of cells, tissues, organs, and chemical signals that helps defend the body from harmful microbes and abnormal cells. It also has to avoid attacking the body's own normal tissues and learn which everyday exposures are harmless.
First-Line Barriers
Skin, mucus, tears, stomach acid, and other barriers prevent many microbes from entering tissues.
Learn MoreInnate Immunity
Innate defenses respond quickly to common signs of damage or infection.
Learn MoreAdaptive Immunity
Adaptive immunity can recognize highly specific molecular targets.
Learn MoreAntibodies
Antibodies are proteins that bind specific molecular shapes.
Learn MoreImmune Memory
Some B and T cells remain after an infection has ended.
Learn MoreVaccines
Vaccines train immune memory without requiring the full disease.
Learn MoreLymphatic System
Lymph vessels and lymph nodes are important immune highways and meeting places.
Learn MoreImmune Balance
A healthy immune system needs both powerful defenses and careful control.
Learn MoreFirst-Line Barriers
These defenses work continuously without needing to recognize a specific species. Normal microbiomes can also compete with potentially harmful organisms for space and nutrients.
Innate Immunity
Cells such as neutrophils, macrophages, and natural killer cells can react within minutes or hours. Inflammation increases blood flow and recruits additional immune cells.
Adaptive Immunity
B cells can develop into cells that make antibodies, while T cells perform several jobs including coordinating responses and destroying certain infected cells.
Antibodies
They can block some microbes or toxins, mark targets for other immune defenses, and help activate additional immune processes. A single antibody recognizes only a limited set of matching structures.
Immune Memory
These memory cells can respond more quickly if the same threat appears again. Immune memory is one of the key ideas behind vaccination.
Vaccines
Different vaccine technologies present harmless pieces, instructions, weakened forms, or inactivated forms related to a pathogen. The immune system learns to recognize important targets and prepares memory cells.
Lymphatic System
Lymphatic vessels collect fluid from tissues and return it to the bloodstream. Lymph nodes filter that fluid and bring immune cells into contact with molecules arriving from nearby tissues.
Immune Balance
Too little immune activity can make infections harder to fight. Too much or misdirected activity can damage normal tissue. Regulatory mechanisms help switch responses on and off appropriately.