eliminating antigens or pathogens. This system is also responsible for
producing the immune response.
There are basically two lines of defense that your body has to protect
itself from foreign substances, including unwanted microorganisms. They are
mechanical (structural defenses) and chemical (mediated defenses).
MECHANICAL DEFENSES (STRUCTURAL)
— Skin, mucous membrane, tears, saliva, stomach acids, urine. Site-specific
protection is affected by the “mucosa immunity system” of the mucosa of the
respiratory, genitourinary, and gastrointestinal lining, which have clusters of
lymphoid cells, including lymphocytes and macrophages.
CHEMICAL DEFENSES (MEDIATORS) — These chemical catalysts are
substances your body uses to bring about an innate immune response. Some
chemicals form barriers in the cell membrane wall to stop invasion by
parasites. Cells also produce enzymes called lysosomes, which are designed
to digest or kill parasitic invaders.
Lysozyme — (enzymes) in tears, sweat and saliva kills various
microorganisms.
Mucus — produced by the mucous membrane, coats and supplies WBCs
that are designed to phagocytize, neutralize or destroy antigens and
pathogens.
Histamine — chemicals (which are released from microorganisms or
damaged cells) that attract leukocytes (white blood cells) for emergency
aid.
Prostaglandins — a biologically active, carbon-20-based unsaturated
fatty acid, metabolized from arachidonic acid. Prostaglandins have a
multitude of functions, including vasodilatation and glucose metabolism.
They are mediators of many chemical processes.
Leukotrienes — promote inflammation by dilation of the vascular system
(capillaries, etc.). They also increase vascular permeability (the ability to
secrete blood, nutrition and immune cells through the walls of the
capillaries, etc.). Vascular permeability allows fibrinogen and proteins to
enter the lymph fluids around a cell. Fibrinogen is converted to fibrin,
which is then used to block off the affected areas. Leukotrienes also
stimulate phagocytosis by macrophages, as well as attract WBCs for
emergency aid.
Interferons — a type of protein that protects cells from viral invasion.
They attach themselves to cell walls, and stimulate that cell’s production