Basic immunology: "Parts of the Immune System

Innate–This is the immune system’s ability to prevent or detect foreign material, then eliminate it without a specific physiological response of the body.
It is the body’s quick and initial response to disease causing organisms (pathogens) which invade our body. The innate response either directly prevents an infection or slows it sufficiently for the slower but more effective and selective adaptive Immune system to activate. But it isn’t a simple system, the innate immune system is extremely complex, consisting of:

Anatomical barriers–These consist of physical barriers. The skin itself is impermeable to pathogens providing defenses like a solid wall. Our nasal passage is lined with mucous that is constantly moved into the stomach catching pathogens and killing them. Our eyes are covered in caustic tears and our mouths in saliva which contains a variety of enzymes. all these ensure that the vast majority of pathogens are killed before they can even enter an area where they can cause harm.

Inflammation–This response include the symptoms we associate with inflammation, fever, swelling, increased blood flow, and other activities, is due to the localized response of the body to the presence of a foreign body or pathogen. It’s main purpose is to provide a physical barrier to control the spread of infection and to heal damaged tissue in the region. Damaged cells release an array of chemical factors which cause pain and blood vessels to become more permeable. This response then attracts phagocytes, cells which recognize and consume foreign or dead tissue. Inflammation is normally a healthy response to injury or pathogen invasion, but in some autoimmune diseases, such as rheumatoid arthritis, it can be painful and debilitating."
Credit:Dr. Dave