Table Of Contents

   General overview
 The basic cells: Leukocytes
    - B lymphocyte cells
    T lymphocyte cells
    - Monocytes
    - Neutrophils
   Fighting off an infection
   Autoimmune diseases

Cell mediated immunity uses the body's cells as the main tools of defense. T cells, which are thymus dependent cells, coordinate the cell-mediated immune system. T-cells originate in such organs as the lymph nodes, thymus, spleen, intestines, and tonsils. T-cells cooperate with B cells to track microorganisms and their path of destruction. Unlike B cells, they can jump out of the body fluids and enter other tissues. There are three different types of T lymphocytes. All are attracted to infected areas and help in the defense of the body.

Killer T cells shoot holes in host cells that are infected and participate in killing and removing foreign particles. Helper Ts help to produce these cells and allow them to multiply by the dozens. Each Killer T carries receptors for one type of antigen. When a Killer T binds to a good number of antigens it puts off a group of substances called lymphokines. Lymphokines cause symptoms like inflammation, swelling and reddening by increasing blood flow in the infected areas. Killers directly attach to the antigens in infected cells and kill them.

Suppressor T cells monitor and adjust antibody levels in the body. They also act as suppressors to counteract the Helper and Killer T cells at the end of infections. In fact, Suppressor Ts turns off active B and T cells once the infection has passed. Hyperactive immune responses, which can cause autoimmune diseases, can be very dangerous to healthy living. Another job of Suppressors is to dampen the immune response when it becomes over active and out of control. Suppressor cells are the last lymphocytes on the scene in an infection.

Helper T cells coordinate the actual immune response of the body; they let other T cells and B cells do their jobs. Helper Ts activate a number of other cells, help to develop plasma cells, release substances that cause B cells to produce antibodies and bind to macrophages, which starts the intercellular communication. A lack of helper Ts can result in a weakened immune response, which allows the body to become infected frequently.


Eosinophils make up about 5% of leukocytes and contain red/orange (when stained) granules containing a compound known as MBP. MBP is toxic to parasites of the body. Eosinophils create the effects of allergic reactions and they defend against parasites.


Only about 1% of leukocytes in the body are basophils. Basophils contain histamines and other compounds, which help in the first stages of infections. They participate only in the immediate immune response to external antigens. They cause reactions as seen in cases of asthma, hay fever, and anaphylaxis. Anti-histamine drugs are made to suppress the allergic reactions of basophils.
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