Immunology is a science that deals with the immune system; the cell mediated and the humoral aspects of immunity. In short, it is a study of immunity to diseases, the antigen/antibody reactions. The exposure of an individual to any infectious agents will normally calls for an immune response, the body's ability to fight off and protect itself from an attack. An elevated white blood cell count usually indicates that an infection is present. There are two categories of immune responses:
1. The Cell-Mediated Immunity - Leukocytes are specialized white blood cells of the immune system that are the first to jump up into action when the body senses the presence of harmful substance. This white blood corpuscles travel through the bloodstream, the lymph, and tissues to defend the body against infections. Leukocytes are also classified: When a white blood cell rid the body of pathogen, it is a phagocyte, the scavenger cells that originate in the bone marrow. And the process of destroying this foreign or harmful substance is called Phagocytosis.
Leukocytes that originate from the thymus gland are called T-lymphocyte cells or T-cells. There are three types of T-cells: these cells acquire specialized functions; the Killer T-cells, Helper T-cells and the Suppressor T-cells. T represents the thymus.
Killer T-cells. These are the lymphocyte cells that attach themselves to an abnormal cells or pathogens killing them by releasing chemical poison, rendering them harmless to the body.
Helper T-cells. These are the watchdogs that are able to recognize the enemies and activate the B-lymphocyte to produce antibodies and help Killer T-cells kill harmful invaders.
Suppressor T-cells slow down the production of B-cells antibodies that help end the immune response.
Natural Killer Cells (NK), originated from the bone marrow. They are the Green Beret like forces that travel though the body identifying, targeting and destroying micro-organisms, cancer cells and cells infected by viruses.
Lymphocytes are the aggressive cells that circulate in the bloodstream and lymphatic system. Lymphocytes include the B-lymphocytes or the B-cells which are formed in the bone marrow, the T-lymphocytes or the T-cells, produced in the thymus and the Natural Killer lymphocytes or NK. In time of infection or disease, the lymph node swells acting as a checkpoint, grabbing and destroying pathogens or antigen as the pass through the lymphatic channels. Lymph nodes are collections of lymphocytes formed into small masses of tissues located in the neck, groins, armpits and abdomen and at the center of he lungs.
Mediator cells monitor the immune activity and send warning signal to slow down blood flow and widen porres in blood vessels to allow fighter cells to get out of the bloodstream and move into battle. Then the Macrophages, the Scavenger cells clean up the debris; bacteria and the dead tissues that are left over after the battle. When the actions of the cells are still insufficient in the battle against the enemies, the harmful invaders; the immune system uses its second line of defense known as the antibodies.
2. Humoral Immunity is much more specific than the Cell Mediated Immunity that each Antibody is effective against the Antigen. An Antigen is any foreign substance that enters the body causing the manufacture of antibodies, also known as IMMUNOGLOBULIN. Antibody (Immunoglobulin)is a protein, smaller than bacteria, (produced by B-lymphocytes) which stick to an antigen releasing chemicals that penetrates its cellular walls and destroys it.
Immunoglobulin also called Immunoglobin and Gamma globulin (antibodies) are powerful, specific, and broad spectrum antiviral and antibacterial medicine currently used in hospitals all over the world to treat a wide variety of infections and diseases.
There are 5 classes of antibodies or Immunoglobulin found in all mammals including humans. They are termed: Immunoglobulin G(IgG), IgM, IgA, IgD and IgE.
IgG is the major antibody class forming about 70% of the total immunoglobulin evenly distributed between the blood and the lymph. It is a protein composed of two or more molecules combined forming a large molecule which can be divided into 4 subclasses, the IgM, IgA, IgD and the IgE.
IgM represents about 10% of total serum immunoglobulin. As a membrane bound molecule it serves as the first line of defense against bacteria and eliminates toxins by stimulating phagocytosis.
IgA forms about 15% to 20% of total serum immunoglobulin acting as one of the frontline defenders of the immune system. It is a major antibody in the mucosal surfaces all throughout the body such as tears, saliva, tracheobronchial secretions, breast milk, and genito-urinary secretions.
IgD represents less than 1% of serum immunoglobulin but it serves to promote the production of antibodies by the B-lymphocytes similar to IgM.
IgE makes up only a trace immunoglobulin in the biody and is found on the cell susrface of mast cells and basophiles in all individuals. Its function is to rid of helminthic parasites (intestinal worms) and protect against allergies.
Immunization is an example of how antigens create specific antibodies to protect the body from infections. Through vaccination, a harmless antibodies toxoid(toxin) in small amount is injected into the body to produce antibodies. Inshort time, these antibodies begin to circulate in the blood providing the body a permanent immunity fron chicken pox, measles, yellow fever or dengue fever. In case of diptheria and tetanus, the immunity may last only a few years. Sometimes a booster shot is needed in later years to increase the amounts of these protective antibodies.
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