The innate immune system is the body’s first line of defense against microorganisms and foreign material. This immune system comes into play immediately/within a few hours of the antigen’s appearance in the body.
This includes physical barriers such as the skin, the respiratory tract, the gastrointestinal tract, and the urinary tract–anything that has contact with the outside world. This also includes chemicals in the blood and immune system cells:
Neutrophils (Shorthand: PMN for polymorphonuclear leukocyte)–Identifies, ingests (phagocytizes), and destroys microbes
Macrophages (Phagocytes) (Shorthand: Mφ)–IIdentifies, ingests (phagocytizes), and destroys microbes
Natural Killer Cells (Shorthand: NK)–Recognizes infected cells and tumor cells and destroys them directly
Dendritic Cells (Shorthand: DC’s)–Secretes chemicals that signal the adaptive immune system
(The shorthand notations are common abbreviations for these cells that you may see in scientific diagrams and notations, including mine.)