Introduction to Immunology Immunity

But if all that is not enough …

• If a pathogen is able to get past the body's nonspecific defenses, the immune system reacts with a series of specific defenses that attack the disease causing agent.
• This is called the IMMUNE RESPONSE
• A substance that triggers the specific defenses of the immune system is known as an antigen.
• An antigen is a substance that a macrophage (wbc) identifies as not belonging to the body.

• The Immune Response involves several organs, as well as White Blood Cells in the Blood and Lymph. These include the BONE MARROW, THYMUS, LYMPH NODES, TONSILS, ADENOIDS, AND SPLEEN.
• Each organ of the immune system plays a different role in defending the body against pathogens.
• Bone Marrow manufactures the billions of WBC needed by the body every day. Some newly produced WBC remain in the bone marrow to Mature and Specialize, while others travel to the Thymus to Mature.
• Lymph Nodes Filter Pathogens from the Lymph and expose them to White Blood Cells
• The Spleen, a fist-sized organ located behind the stomach, Filters Pathogens from the Blood. It is stocked with WBC that respond to the trapped pathogens.

• The Immune Response

Lymphocytes

• The white blood cells of the immune system are known as Lymphocytes. These WBC
• are also found in the spleen and blood.
• Lymphocytes are wbcs that activate the immune response. There are two main
• types of lymphocytes: b cells and t cells.
• B-LYMPHOCYTES (B cells), Which are produced and matured in the
• bone marrow, are responsible for producing antibodies.
• Antibodies are special proteins that can bind to the antigen on The surface of a
• pathogen and help destroy it.

Self/Non-self Distinction

• In order to Respond to Pathogens, but to avoid responding to and
• destroying cells from its own body, Lymphocytes
• Must be able to recognize a pathogen as a foreign invader and
• distinguish it from cells of the body.