Lymphatic tissues, including the spleen, thymus gland and lymph nodes,
are responsible for the growth, maturation and activation of your white blood
cells. The growth and function of immune cells are regulated by cytokines,
which are protein in nature and act as growth mediators. There are over 100
different types of cytokines produced by your WBCs. These include your
interleukins, interferons, tumor necrosis factor, etc.
Let’s examine some of the most important immune cells that your body
uses to defend itself. Macrophages are monocytes that have left circulation
and have settled and matured in tissues. Macrophages are found in large
numbers in the tonsils, spleen, and lymph nodes. Fifty percent or more of the
body’s macrophages are found in the liver and are called Kupffer cells.
However, they are found everywhere, including the brain and blood. They
act as scavengers, cleaning as they go. Macrophages and neutrophils are the
master phagocytic (ingesting and destroying) cells of your immune system.
Natural killer (NK) cells are a type of lymphocyte processed in the bone
marrow, which accounts for 1-5 percent of all lymphocytes. They are
considered the masters of the immune cells. Their job is to destroy tumor or
virus-infected cells. These are a part of your innate immunity because they do
not respond to memory, and are not specific in their response. They only
recognize a specific class, not a specific type of cell.
Summary: The Immune System
Your body is naturally designed to protect itself from invaders, including