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The Immune SystemA look inside your body’s defense system…
By: Jay BrennanKayla Gomez
Alex MucciAndrew Wabunoha
OverviewThere 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 shouldn’t 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, that’s 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 lymph
These 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 Leukocytes
Leukocytes: White Blood CellsInnate Leukocytes: the phagocytes
Neutrophils Macrophages Dentritic cells Mast cells Natural Killer (NK) cells
Phagocytosis 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, tonsils and thymus where 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 doesn’t 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- ¾ 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 body’s 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 and eosinophils.
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 SclerosisAddison’s DiseaseLupusJuvenile Rheumatoid Arthritis and PsoriasisSclerodermaUlcerative Colitis and Crohn's disease
ImmunodeficiencyThese are caused by inherited genetic
diseases. People are born without some of the body’s 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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