Innate Immune System
If foreign particles make it past the skin, macrophages will devour them through phagocytosis. Macrophages are called to the site of inflammation by chemicals such as histamine, which causes vasodilation, inflammation and allows macrophages to move out of the blood steam and into the tissues.
Granulocytes, such as neutrophils, eosinophils, and basophils are examples of a macrophage called in this manner. Macrophages work well against extra cellular pathogens such as bacteria. These responses are carried out without learning and are nonspecific immune responses.
Another type of macrophage is a granular such as lymphocytes, which are cells that originated in bone marrow and matured in the spleen and lymph nodes. They are responsible for antibody production, immune system modulation and the targeted killing of infected cells.
Monocytes are another type of macrophage and much like a garbage truck, just picks up the debris left behind through endocytosis (phagocytosis)
There are several other mucous membranes such as in the eye and oral cavity that produce a non-specific bactericidal enzyme called lysozyme, which is secreted in both tears and saliva. This helps guard against potential pathogens entering from the eye or the mouth. The acidity of the stomach also helps to neutralize pathogens.
Infected immune cells and normal somatic cells can produce interferon, a non-specific defense protein that prevents viral replication and dispersion. It is directed against viruses but not against specific viruses. This is all part of the innate immune system. Interferon does not have to know a virus to kill it, it is good from the start against a majority of viruses so it didn’t adapt.