The Immune System: Information about Lymphocytes, Dendritic Cells, Macrophages, and White Blood Cells

The Immune System

The Immune system is a complex network of cells (such as lymphocytes) and organs that work together to defend the body against foreign substances (antigens) such as bacteria, a virus or tumor cell.  When the body discovers such a substance several kinds of cells go into action in what is called an immune response.  Below is a description of some of the cells that are part of the immune system.

Lymphocytes

Lymphocytes are one of the main types of immune cells.  Lymphocytes are divided mainly into B and T cells.

• B lymphocytes produce antibodies - proteins (gamma globulins) that recognize foreign substances (antigen) and attach themselves to them.  B lymphocytes (or B cells) are each programmed to make one specific antibody.   When a B cell comes across its triggering antigen it gives rise to many large cells known as plasma cells.  Each plasma cell is essentially a factory for producing antibody.  An antibody matches an antigen much like a key matches a lock.  Whenever the antibody and antigen interlock, the antibody marks the antigen for destruction.  B lymphocytes are powerless to penetrate the cell so the job of attacking these target cells is left to T lymphocytes. 
• T lymphocytes are cells that are programmed to recognize, respond to and remember antigens.  T lymphocytes (or T cells) contribute to the immune defenses in two major ways. Some direct and regulate the immune responses.  When stimulated by the antigenic material presented by the macrophages, the T cells make lymphokines that signal other cells.   Other T lymphocytes are able to destroy targeted cells on direct contact.

Macrophages

Macrophages are the body's first line of defense and have many roles.  A macrophage is the first cell to recognize and engulf foreign substances (antigens).  Macrophages break down these substances and present the smaller proteins to the T lymphocytes.  (T cells are programmed to recognize, respond to and remember antigens).  Macrophages also produce substances called cytokines that help to regulate the activity of lymphocytes.

Dendritic Cells

Dendritic cells are known as the most efficient antigen-presenting cell type with the ability to interact with T cells and initiate an immune response.  Dendritic cells are receiving increasing scientific and clinical interest due to their key role in the immune response and potential use with tumor vaccines.

White Blood Cells

There are different types of white blood cells that are part of the immune response.  Neutrophils or granulocytes are the most common immune cells in the body.  With an infection, their number increases rapidly.  They are the major components of pus and are found around most common inflammations.  Their job is to eat and destroy foreign material.  Basophils and eosinophils are white blood cells that contain large granules inside the cell.  They interact with certain foreign materials.  Their increased activity may lead to an allergic reaction.

The immune response is a coordinated effort.  All of the immune cells work together, so they need to communicate with each other.  They do this by secreting increased levels of a special protein molecule called cytokines that act on other cells.  There are many different cytokines.  Examples of these are interleukins, interferons, tumor necrosis factors, and colony-stimulating factors.  Some immunotherapy treatment strategies involve giving larger amounts of these proteins by an injection or infusion.  This is done in the hope of stimulating the cells of the immune system to act more effectively or to make the tumor cells more recognizable to the immune system.

Caution: There are people who promote unproven therapies as immune system boosters.  Be careful when evaluating these claims.  The following are types of immunotherapies that are commonly and legitimately used in traditional and scientific medical practice.

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