Terms about immunology and inflammation

Term	Definition
Lymph	Tissue fluid that is being drained away to prevent its accumulation and swelling of the tissues
Edema	Swelling usually caused by the accumulation of tissue fluid
Lymph vessels	Microscopic tubes that drain the lymph out of the tissues
Lymph nodes	Bean-like structures that the lymph vessels empty into. These contain white blood cells, which will kill infectious organisms in the lymph.
Leukocytes	Means ‘white blood cells,’ but usually refers to the white blood cells involved in the inflammatory or innate immune system rather than those in the lymph nodes.
Granulocytes	The white blood cells which contain granules of chemicals which can be released to help fight off infectious organisms
Neutrophils or polymorphonuclear leukocytes	The commonest white blood cells in the blood. They contain granules that are ‘neutral’ in pH. Their other name means they have nuclei of many shapes. They eat invading organisms.
Basophils	White blood cells with basic granules. They can move into infected tissues and release the compounds in their granules.
Eosinophils	White blood cells whose granules stain with eosin. They are produced to fight off parasites.
Mast cells	These are like basophils, but they are stationary and live in the tissues as a kind of ‘early warning’ system.
Monocytes or macrophages	These are called monocytes when they are in the blood. When they crawl into the tissues they develop lots of tentacles and are then called macrophages. They eat invading organisms and release many chemicals.
Phagocytosis	When cells engulf and digest invading organisms or cell debris.
Chemical mediators of inflammation, or inflammatory mediators	Chemicals released by white blood cells, or injured tissue cells. They increase blood flow and fluid movement into an injured area, attract more WBCs, and may cause signs like rash and fever.
Innate immunity	The automatic mechanisms that prevent infections. They include the leukocytes and the inflammatory mediators they release. They react the same way to any kind of infectious organism.
Adaptive or specific immunity	The immune mechanisms that target specific diseases. These are what make you ‘immune to’ something.
Antigen	This is the protein on the surface of an infectious organism that your body uses to identify it, so the specific immune response can kill it.
Antigen-presenting cells	These are macrophages or dendritic cells. They eat the infectious organism and carry the antigens from its surface to the lymphocytes, which will then start a specific immune response against it.
lymphocytes	The WBCs living in the lymph nodes. Some also circulate in the blood. These are responsible for specific immunity.
T-helper cells	These are the lymphocytes that start the specific immune response. They identify that the antigen is really foreign rather than being part of your body, and tell the other lymphocytes it is OK to attack it.
T-killer cells	These lymphocytes specialize in killing body cells that have become infected with viruses.
B cells	These make chemicals to attach to and kill specific antigens.
Antibodies	These are the chemicals the B cells make to kill specific antigens.
Active immunity	Immunity caused by the presence of B memory cells against an antigen.
Passive immunity	Immunity caused when someone is given antibodies against an antigen, but does not have their own activated B or T cells and cannot make their own antibodies against the antigen. This is only temporary protection.