Within the blood, there are red blood cells and white blood cells. The white blood cells are immune cells. White blood cells can be divided into two groups: B cells, coming from bone marrow, and T cells, which are trained within the thymus to combat foreign invaders. (the T cell is located in the center at the B cells)

Throughout the lifetime of a person, the B cell is capable of producing one billion different antibodies to combat viruses, bacteria, or any other type of pathogen.

A natural killer cell ( " kiss of death '' ) between two large cancer cells.

The natural killer cell destroying a cancer cell.

Natural killer cells have the ability to kill any type of cancer cell. While natural killer cells neutralize cancer cells safely and without side effects, chemotherapy and radiotherapy kill cancer cells and healthy cells including immune cells-thus lowering a patient's resistance to illness and infection.

Viewed under an electron microscope, this macrophage or "garbage man of the body", is ingesting foreign particles which have entered the body.

One of the main functions of the macrophage is to ingest any foreign particles, including aged body cells.

The macrophage has tentacles to actually grab a particle and engulf it, as in these photos.

In these photos, the macrophage is engulfing the captured bacteria.