Innate Immune System

    The innate immune system is the immune system that a person has at birth, and changes little in a person's life.        This immune system protects the body by recognizing the general characteristics of pathogens. For example, the mechanical barrier effect of the skin can prevent a variety of organisms from entering the body. Innate immune cells can recognize the general characteristics of pathogens, such as the cell wall of bacteria, but these cells cannot distinguish different types of pathogens. Using military analogy, the innate immune system is like using the same type of missile to shoot at different targets, rather than using different types of missiles for different types of targets. For example, macrophages participate in the innate immune response by finding, eating, and killing different types of bacteria. Natural killer cells (NK) are another type of immune cells that can eliminate cells infected by viruses or cancer cells. 1

    The innate immune system is composed of many different components. Although the innate immune system is also called "non-specific" immunity, this name is not very accurate. The following figure shows the immune response of the innate immune system to certain types of biological or non-biological "invaders". When a creature or substance invades the body, it must bypass some physical and chemical barriers. Our skin is like a tough and flexible shield that can deter many kinds of invaders. Skin mucus is the body's first line of defense, including mouth, nose, anus, vagina and ear wax. They can block bacteria, dust and other particles. Body secretions such as gastric acid, salivary protein, and tear protein can also provide a barrier. Hair prevents larger creatures from touching the skin. If invading organisms or particles pass these barriers (such as a thorn), macrophages and neutrophils will be produced in the bone marrow to attack foreign objects. To

    The figure below shows some of the components of the human innate immune system.