Skin is the most obvious part of the immune system, acting as a primary barrier between germs and your body. Our skin is tough and generally impermeable to bacteria and viruses. Other components of the immune system are  the thymus, spleen, lymph system, bone marrow, white blood cells, antibodies, compliment system, interferons and hormones.

The thymus, located between the breast bone and heart is important for producing T-cells and is very important in newborn babies. The spleen filters the blood looking for foreign cells as well as for old red blood cells in need of replacement.

Lymph or blood plasma bathes the cells with water and nutrients. The lymph system drains and filters these fluids to detect and remove bacteria. Bone marrow produces new blood cells, both red and white from stem cells.

The white blood cells are the most important part of the immune system. They  are actually a whole collection of different cells that work together to destroy bacteria and viruses. Antibodies are produced by white blood cells.

Antibodies can bind to an invader and signal to the complement system that the invader needs to be removed. The complement system, like antibodies, is a series of proteins. Complements, manufactured in the liver, cause lysing (bursting) of cells and signal that a cell needs to be removed.

Some hormones generated by components boost the immune system. These hormones are known generally as lymphokines. Interferons, like antibodies and complements, are proteins, and their job is to let cells signal to one another.