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Nonspecific Defenses are the body's first line against disease. They are not directed against a particular pathogen. They guard against al.
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Passive Immunity- Immunity that is obtained from a
outside source. Example: Antibiotic, Clostrum
Active Immunity- Immunity that is obtained from the
immune system actively defending the body.
Example: Vaccines, Immunity after having a disease
The Body's MOST IMPORTANT Nonspecific Defense is the SKIN. UNBROKEN Skin provides a continuous layer that protects almost the whole body. Very Few Pathogens can penetrate the layers of dead cells at the skin's surface. Oil and sweat glands at the surface of the skin produce a salty an acidic environment that kills many bacteria and other microorganisms. The importance of the Skin as a Barrier against Infections becomes obvious when a small portion of skin is broken or scraped off: Infection almost always follows. Infections are a result of the penetration of the broken skin by microorganisms normally present on the unbroken skin. Pathogens also enter the body through the Mouth and Nose, but the body has Nonspecific Defenses that protect those openings.
The most common Phagocyte, 50 to 70 percent of the White Blood Cells in the body, is the NEUTROPHIL. Neutrophils circulate freely through blood vessels, and they can squeeze between cells in the walls of a capillary to reach the site of infection. They then engulf and destroy any pathogens they encounter
Inflammatory Response Continued
Another type of Phagocyte (also a White Blood Cell) is the MACROPHAGE ; they consume and destroy any pathogens they encounter, they also rid the body of worn out cells and cellular debris. Some Macrophages are stationed in the tissues of the body, awaiting pathogens, while others move through the tissues and seek out pathogens.
Inflammatory Response Continued
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.
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
Something has got through the first lines of defence, and entered the body in force.
B-cell or T-cell
Surface receptor molecule
Nasty thing This lymphocyte recognises the red pathogen
B-cell or T-cell
This one doesn’t
In addition, B-Cells (but not so much T cells) also undergo somatic
hypermutation. Somatic just means in the body, during one’s lifetime.
Hyper just means `a lot’. In a nutshell:
A pathogen comes along: If it gets through the barriers (skin, etc), nonspecific lymphocytes kill it, as part of the `inflammation’ response in reaction to injury. If it gets past that (I.e. there’s so much of it, it gets into the bloodstream anyway), then the Immune Response comes into play, as follows: If we’ve seen this one before , there are antibodies in the blood (secreted by memory cells); these antibodies disable and/or tag the invader. The tagging attracts killer cells to make sure it is destroyed. If we haven’t seen this before , B-cells and T-cells are floating around with a great variety of surface receptors. One of these will at least recognise it a bit. Clonal expansion then happens, and with gene variability and somatic hypermutation we eventually get some B or T cells which are capable of recognising it. The associated antobodies then disable and tag the invaders.