The immune system is a network of biological systems that protects an organism from most pathogens, and therefore diseases.
The immune system detects and responds to a wide variety of pathogens that distinguish from the organism’s own healthy tissue.
The innate immune system provides a preconfigured response to broad groups of situations. In contrast, the adaptive immune system provides a tailored response to each situation by learning to recognize molecules it has previously encountered.
innate immune system
The innate immune system provides a preconfigured response to broad groups of situations.
For the innate immune system to work, it needs to have a mechanism by which it can identify pathogens. So cells of the immune system have receptors that detect what is not part of the organism.
These are the cells in the innate immune system, in humans.
Cells that eat things are called phagocytes.
macrophage
Macrophage are phagocytes. These cells ingest pathogens, particularly bacteria. Once the pathogens have been gobbled up, they are destroyed inside the macrophage.
neutrophil
Neutrophils are phagocytes. Also they are the most abundant cells in the immune system. Unfortunately, neutrophils are a little worse at eating and will die once they have ingested a pathogen.
mast cell
Mast cells respond to certain kinds of pathogens (e.g. worms). They are important in their role in creating allergic responses. They release a chemical called histamine, to cause allergy symptoms like inflammation.
eosinophil
Eosinophils are similar to mast cells, but very little is known about them.
natural killer cell
Natural killer cells help to clear viral infections. Viruses tend to end up inside cells, so natural killer cells find tell cells with viruses in them to self destruct.
dendritic cell
Dendritic cells gobble up stuff from the environment around them and them on their surface.
adaptive immune system
The adaptive immune system provides a tailored response to each situation by learning to recognize molecules it has previously encountered.