Innate immunity is present at birth and includes the skin, mucous membranes, and white blood cells that fight pathogens. It is different from acquired immunity, which is created when the immune system fights a pathogen and creates antibodies. White blood cells have different roles in the innate immune system, including killing bacteria and viruses. Innate immunity also has the ability to form new immunities to specific pathogens.
Innate immunity refers to those characteristics of immunity that are present at birth and passed down genetically from parents to offspring. It consists not only of the skin and mucous membranes, but of the blood cells responsible for fighting pathogens such as bacteria and viruses. Innate immunity is different from acquired immunity, which is not present at birth and occurs when the immune system fights a pathogen and creates antibodies against that pathogen to provide future immunity.
The first important element of the innate immune system is the skin. Most pathogens cannot penetrate the skin unless the integrity of the barrier has been compromised by injury. Ciliary action in the lungs and nasal passages helps expel pathogens from the body before they can cause disease. Tears, saliva, urine, and the sloughing off of dead skin cells are all innate immune functions that help keep pathogens from infecting the body. The mucous lining of the digestive and respiratory tracts also traps pathogens before they have a chance to gain a foothold in the body and cause disease.
White blood cells are one of the most important features of innate immunity. The different types of white blood cells include phagocytes, macrophages and natural killer cells. White blood cells serve the immune system by identifying and eliminating pathogenic threats. These cells kill bacteria and viruses.
Different types of white blood cells have different roles in the innate immune system. Macrophages develop when monocytes, a type of white blood cell that travel in infected tissue, grow larger and filled with enzymes that help them kill bacteria. The macrophages stay in the tissue at the site of infection, removing the damaged bacteria and dead cells.
Other white blood cells of the immune system have different abilities to trap, kill, ingest and digest pathogens. Basophils, a type of white blood cell implicated in allergic reactions, release histamine when they encounter allergens. Histamine increases blood flow to infected tissue, allowing other white blood cells a better opportunity to remove invading pathogens. Dendritic cells, found in lymph nodes and skin, help break down antigens so that T cells can recognize and eliminate them. Natural killer cells can eliminate viruses by killing the cells they infect.
Innate immunity comes with the built-in ability to form new immunities to specific pathogens. The white blood cells and blood proteins of the innate immune system are responsible for the body’s ability to acquire immunity. Acquired immunity occurs when white blood cells create antibodies against a particular pathogen, making the individual immune to disease from that pathogen in the future. Acquired immunity is often induced through the use of vaccinations.
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