Immune System
The immune system
The immune system is the system of specialized cells and organs that protect an organism from outside biological influences. (Though in a broad sense, almost every organ has a protective function - for example, the tight seal of the skin or the acidic environment of the stomach.)
When the immune system is functioning properly, it protects the body against bacteria and viral infections, destroying cancer cells and foreign substances. If the immune system weakens, its ability to defend the body also weakens, allowing pathogens, like the common colds and flu, to grow and flourish in the body. The system also performs surveillance of tumor cells, and immune suppression has been reported to increase the risk of diseases.
The immune system is often divided into two sections:
Innate Immunity: Comprised of hereditary (always there) components that provide an immediate "first-line" of defense to continuously ward off pathogens.
Adaptive (acquired) Immunity: By manufacturing antibodies (a type of protein) and T-cells specifically designed to target particular pathogens, the body can develop a specific immunity to particular pathogens. This response takes days to develop, and so is not effective at preventing an initial invasion, but it will normally prevent any subsequent infection, and also aids in clearing up longer-lasting infections.