The Immune System

The Immune SystemA look inside your bodys defense systemBy: Jay BrennanKayla GomezAlex MucciAndrew WabunohaSneak peakhttp://kidshealth.org/kid/htbw/ISmovie.htmlOverviewThere are multiple cells, tissues, and organs involved in the immune system.All living organisms, including viruses, have a rudimentary immune system.Allergies are caused by an over-reaction by the immune system to something that shouldnt otherwise be harmful.Some diseases affect the immune system specifically.Two major subdivisions of the immune system: innate or non-specific immune system and the adaptive or specific immune system.Dual NatureAntigen-specific- recognize and act against particular antigens.Antigen- anything that elicits an immune response.Allergen- a simple substance, thats not normally an antigen (pollen), that elicits allergies.Systemic- not confined to the initial infection site, but work throughout the body.Memory- recognize and mount an even stronger attack to the same antigen the next time.

TransportationTwo main fluids: blood and lymphThese are responsible for carrying immune agents throughout the body.White blood cells- transported by blood.

What is the Lymphatic systemThroughout the body and helps clear the body of all foreign material.

The blue in the figure shows the location of lymph nodes.

What your body protects against Viruses Fungus Bacteria PollenAnd much more

Layered defenseThe body employs more specifically defined responses to fight off pathogens.There are three main defenses:Surface defensesThe Innate Immune SystemThe Adaptive Immune System Surface DefensesPrevents entry to viruses and bacteria.Could be: skin, a shell, exoskeletons, etc.However, does not have to be the outside of a body.For example: mucus is secreted by the sinuses to entrap microorganisms.Tears are also a mechanical response to flushing pathogens from the eyes.

Surface Defense EnzymesThe body also secretes certain enzymes as a first level of defense from pathogens.These form chemical barriers.Antimicrobial- B-Defensin is secreted by the skin and respiratory tract.Antibacterial- lysozyme and phospholipase A2 in saliva, tears, and breast milk.Innate Immune System (IIS)This is the layer you most normally think about when you think of the immune system, as it contains most of the cells.This is also because it is the dominate layer.This is the first layer of defense once a pathogen gets into the body.Triggered by pattern recognition receptors, which recognize the chemical signature of a broad spectrum of pathogens, or when infected/damaged cells send a distress signal.Non-specific response, meaning it tackles all pathogens the same.InflammationOne of the first responses by the IIS caused by blood flowing into tissue.Caused by the release of eicosanoids and cytokines, which are released by infected/damaged cells.Attract Leukocytes (White Blood Cells) to the area via the influx of blood.

Compliment SystemA series of over 20 different proteins that attacks an infected area .Compliments the attack by helping antibodies and other cells.Most proteins are stored in the liver.This is the major hormonal response of the IIS.

Cellular DefensesConsists of the cells that attack and destroy the invading pathogens.Two main types: Leukocytes and Innate LeukocytesLeukocytes: White Blood CellsInnate Leukocytes: the phagocytes NeutrophilsMacrophagesDentritic cellsMast cellsNatural Killer (NK) cellsPhagocytosis is the process in which a phagocyte eats and destroys a pathogen.Important mediators in the activation of the Adaptive Immune system.

Leukocytes (White Blood Cells)Single most important cell of the Immune system.Act like independent, single-celled organisms.Approximately 7000 White Blood Cells per liter of blood (about 1% of the cells in the blood.An increase over this limit is called Leukocytosis and a decrease is called Leukopenia.This is linked to types-of-diseases such as autoimmunity and immune-deficiency.

PhagocytesMany different types with many different roles.Neutrophils and Macrophages patrol the body and seek out potential pathogens.Neutrophils are the most abundant leukocyte, typically making up between 50-60% of the circulating population.During inflammation, Neutrophils are typically the first responders due to a process called chemotaxis.Macrophages are more likely to stay in one spot while acting as enzyme producers. They also act as scavengers ridding the body of worn-out cells.Phagocytes cont.Dentritic cells: Are found in the external environment to the body (skin, nose, lungs, and intestines).Named for their resemblance to Neuronal dentrites .Are a key to activating the Adaptive Immune System by passing the antigen-information to T cells.Mast cells:Reside in connective tissue and mucus membranes.Secrete chemicals that defend against parasites and are active in allergic responses, such as asthma. Natural Killer (NK) cellsType of cytotoxic lymphocyte (meaning they are a white blood cell with small granules in their cytoplasm contain special proteins such as perforin and proteases known as granzymes.)Important to the innate immune systemImmediate response to viral infected cells and tumor formation. It acts about 3 days after infection.Named natural killers due to the fact that they do not need any activation to kill cells missing markers of MHC (major histocompatibility complex) class 1.The granzymes enter into the target cell after the perforin creates pores in the [target] cell, causing apoptosis.

Natural Killer (NK) cells cont.Apoptosis- Destruction of the virus inside.Cell lysis- Lysing would cause only the release of virions.Purpose is to contain viral infections while the adaptie immune system generates antigen-specific cytotoxic T cells that clear the infection.NK differ and mature in the bone marrow,lymph node,spleen,tonsilsandthymuswhere they then enter into the circulation.Lack of NK cells makes you susceptible to early phases of herpes virus infection.

Adaptive Immune SystemAlso known as the acquired immune system or the specific immune system.Cell-mediated and antibody responses carried out by different lymphocyte cells, B cells and T cells.Antibodies need B Cells in their creation so they can circulate in blood plasma and lymph to bind to foreign antigens. Antibodies are immunoglobulins, large Y-shaped proteins; typically composed of two large heavy chains and two small light chains.Cell-mediation doesnt involve antibodies but requires the activation of macrophages, natural killer cells (NK), antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.Adaptive Immune System cont.T cells recognize specific molecules (of a virus) and become activated.Adaptive immune system remembers a pathogen its encountered before; this is called immunologic memory.Adaptive immune system needs help from other cells, such as receptors to recognize their designated, specific substance. Macrophages eat whatever they do not recognize, breaking it down to basic proteins before presenting them to the immune system.T Cells80% of all lymphocytes are T cells.Named T cells because they mature in the thymus, a gland in the chest.Three types (these play a role in the destruction of problem cells in the body):Cytotoxic T cells- require activated APCs, and rely on helper T cells. Prepares for the destruction of their target.Suppressor T cells- Can suppress both functions of cytotoxic and helper T cells. Protects body against autoimmune attacks.Helper T cells- of T cell population. Release lymphokines to help control parts of the immune system through the growth of other T cells to attack foreign substances.

T Cells Cont.Start out as stem cells produced by bone marrow.They then go to the thymus for maturity for three weeks.99% do not make it to maturity, due to the body needing perfect T cells in order for the bodys own cells not to be attacked by the T cells. They then are given a receptor, which have several different types. These distinguish what type of T cell it will be, its role, and which cells it can interact with.Roles and functions:Signaling for growth and activation of B cells.Activation of cells that can 'eat' foreign substances.Stimulation of cytotoxic T cells during a viral infection.Signaling growth in cells, including other T cells, macrophages andeosinophils.

T Cells Cont.APC (antigen presenting cells) identify foreign substances, eat them, and then present part of it to the T cells so it can respond by releasing many T cells of different types into the blood stream, which destroy the foreign substances. APC have a special molecule on their surface to communicate to the T cells.Autoimmune DiseasesAsthmaType I DiabetesLeukemiaMultiple SclerosisAddisons DiseaseLupusJuvenile Rheumatoid Arthritis and PsoriasisSclerodermaUlcerative Colitis and Crohn's diseaseImmunodeficiencyThese are caused by inherited genetic diseases. People are born without some of the bodys immune defenses.Chronic Granulomatous Disease (CGD)Common Variable Immunodeficiency (CVID)DiGeorge Syndrome (DGS)Selective IgA DeficiencySevere Combined Immunodeficiency (SCID)X-Linked Agammaglobulinemia (XLA)

AllergyAn allergy is an abnormal reaction to a relatively harmless antigen.Seasonal allergiesPerennial allergiesFood allergies

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