The Immune System -- An Overview Check out healingifts' natural herbal products to protect you and maintain your immune system !

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The Immune Response An immune response to foreign antigen requires the presence of an antigen-presenting cell (APC), (usually either a macrophage or dendritic cell) in combination with a B cell or T cell. When an APC presents an antigen on its cell surface to a B cell, the B cell is signalled to proliferate and produce antibodies that specifically bind to that antigen. If the antibodies bind to antigens on bacteria or parasites it acts as a signal for pmns or macrophages to engulf (phagocytose) and kill them. Another important function of antibodies is to initiate the "complement destruction cascade." When antibodies bind to cells or bacteria, serum proteins called complement bind to the immobilized antibodies and destroy the bacteria by creating holes in them. Antibodies can also signal natural killer cells and macrophages to kill viral or bacterial-infected cells.

The Organs of the Immune System

Bone Marrow -- All the cells of the immune system are initially derived from the bone marrow. They form through a process called hematopoiesis. During hematopoiesis, bone marrow-derived stem cells differentiate into either mature cells of the immune system or into precursors of cells that migrate out of the bone marrow to continue their maturation elsewhere. The bone marrow produces B cells, natural killer cells, granulocytes and immature thymocytes, in addition to red blood cells and platelets.

Thymus -- The function of the thymus is to produce mature T cells.

Lymph Nodes -- The lymph nodes function as an immunologic filter for the bodily fluid known as lymph. The Cells of the Immune System

T-Cells -- The main function of the T helper cell is to augment or potentiate immune responses by the secretion of specialized factors that activate other white blood cells to fight off infection.

Natural Killer Cells -- They function as effector cells that directly kill certain tumors such as melanomas, lymphomas and viral-infected cells, most notably herpes and cytomegalovirus-infected cells.

B Cells -- The major function of B lymphocytes is the production of antibodies in response to foreign proteins of bacteria, viruses, and tumor cells. Antibodies are specialized proteins that specifically recognize and bind to one particular protein that specifically recognize and bind to one particular protein.

Granulocytes or Polymorphonuclear (PMN) Leukocytes -- These cells are predominantly important in the removal of bacteria and parasites from the body.

Macrophages -- They are often referred to as scavengers or antigen-presenting cells (APC) because they pick up and ingest foreign materials and present these antigens to other cells of the immune system such as T cells and B cells.

Dendritic Cells -- Dendritic cells, which also originate in the bone marrow, function as antigen presenting cells (APC).