The Immune System
ATS Unit 7
Learning Goals
• Discuss the functions of the immunes system. • Differentiate between mechanisms of specific
and nonspecific immunity. • Identify functions of various immune cells and
proteins. • Immune cells are produced by the bodies
lymphatic tissues.
Thoughts on Immunology
• This science is very new. – We are still earning the complexities of how
immune cells form, interact, and change throughout life.
– This stuff can be confusing. We will take it one step at a time. We will start simple and build up.
Functions of the Immune System
• The immune systems’ job is to protect the body against disease and damage from pathogens. – This includes microbial pathogens, allergens, toxic
chemicals, and malignant cells (cancer). – Functions are broken down into specific and
nonspecific defense. – Further broken down into cellular and humoral
immunity.
Specific vs. Nonspecific Immunity
Nonspecific• Does not require any
adaptation. • We are born with these
responses. • The defenses are general
(they can attack lots of different antigens).
• Act immediately, do not require time to develop.
Specific• We “learn” these defenses
via exposure to antigens. • The defenses are meant for
only one antigen. • Takes time to build up in
system, and may decrease over time with no repeat exposure.
THE NON SPECIFIC IMMUNE DEFENSES
Key Points
• NONSPECIFIC defenses are defenses that are general (not aimed at specific factors). – This includes defense in the skin, mucous
membranes, respiratory, digestive, urinary and reproductive tracts to prevent disease.
– Also include the inflammatory response and nonspecific cells that attack antigens.
The Innate Response System
• The nonspecific defenses are known as this because they do not take any adaptations or “learning” to act.
• Can respond to antigens without knowing what exactly they are.
• Two “lines” of Defense
1st Line Defense
• These are our Barriers which are always active. – Skin– Chemical Barriers (stomach acid, skin oil, mucous
in respiratory system, urinary tract, digestive system, etc.
– Sneezing, coughing
2nd Lines of Defense
• Two parts: – Inflammatory Response (the “battlefield”)• An nonspecific response to injury or antigen. • Causes a tissue response, brings in reinforcements to
deal with antigens. – Phagocytes• Cells that “eat” antigens – recognizes lots of different
types of foreign particles and organisms. • Basically attacks anything they can identify as shady or
out of place.
Inflammatory Response
• This is mediated by both special immune cells located in the tissues, and by elements in the blood.
• Inflammation is a natural response to injury and/or irritation.
• Regulated by: – Certain types of white blood cells– Chemicals such as histamines
Inflammatory Response
Signs• Redness near the injury• Swelling (edema) via
vasodilation and increased permeability.
• Increased blood flow• Increased presence of
immune cells. • Pain
Functions• The increased circulation
allows the important protective cells to reach the site of injury.
• Swelling and pain help to protect the injury.
Inflammatory Response
Special Cells in the Nonspecific Defenses
• Phagocytes – “eat” or destroy pathogens and dead cells– Macrophages move in and out of the blood stream to eat up
harmful cells. – Neutrophils dump chemicals onto harmful cells to dissolve
them. • Basophils and Eosinophils – release chemicals called
histamines and other toxins to destroy pathogens (can also harm body’s own tissue).
• Natural Killer Cells – kill body’s cells that have been compromised, whether by mutation or by viral infection.
SPECIFIC IMMUNITY
Key Points
• Again, these types od defenses must be “learned” throughout life.
• They respond to “specific” antigens. • Body develops memory after initial exposure
to react in future encounters.
Immunoglobulin (Antibodies)
• There are 5 types: IgG, IgA, IgM, IgD, IgE• Each responds to a different type of antigen. • These do not kill microbes or remove them,
they just mark them. • IgG is the most abundant, is found in blood and
lymph and is active against most microbes. • IgE is active in response to allergens. .
Antigen-Antibody Reactions
• Antigens are proteins that attach themselves to antigens.
• By doing so, they may mark the pathogen for disposal, or just prevent it from binding with other body cells.
Cells of Specific Immunity
• These are produced in Lymphatic Tissue (more on that later). – Most functions are regulated by two types of cells. • B Lymphocytes• T Lymphocytes (Helper, Killer, and Suppressor)
– Other cells include macrophages and plasma cells that are activated by action in the B and T cells.
First Steps Toward Adaptive Immunity
• Initially, triggered by a response from the nonspecific system, which initially marks the antigen as “foreign and dangerous”: – Nonspecific responses, such as phagocytes, attack
and kill antigens. – In the meantime, Helper T Lymphocytes release
chemicals to stimulate the formation of specific antibodies.
Lymphocyte Action
T Lymphocytes• T for Thymus• Stimulates creation of:
– Killer T Cells – kill marked pathogens.
– Memory T Cells – hang out in the body, ready to recognize the infection again.
B Lymphocytes• B for Bone Marrow• Stimulates the creation of:
– Plasma Cells – secrete antibodies against the specific antigen. (remember antibodies mark the antigen for destroying)
– Memory B Cells - hang out in the body, ready to recognize the infection again.
Subsequent Encounters with Known Pathogens
• Initial immunity takes several days to develop (why we get sick)
• After that, the T and B lymphocytes that serve as memory cells quickly respond and create lots of antibodies and killer T cells to get rid of the antigen.
Acquiring Immunity
Active• Our bodies go though the
whole process of lymphocyte stimulation, antibody production, etc.
• It is typically long lasting. • We get in naturally from
actual illness/infection. • We can get it artificially via
vaccines.
Passive• Immunity we borrow from others. • Our bodies do not develop
memory cells in this situation. • We only get the antibodies to
fight the present infection. • We get this naturally via our
mother’s placental blood before birth and breast milk in infancy.
• We get this passively via injected antitoxins or immunoglobulin infusions.
Autoimmunity
• Sometimes, mechanisms in the body can become confused and attack cells that are not foreign or pathogenic. – We call the autoimmunity. Diseases in this class
include lupus, Type 1 diabetes, Crohn’s Disease, MS and many more.
– It may cause the body to attack one type of tissue or several.
– Treatments focus on decreasing the body’s immune response.
Hypersensitivity
• Sometimes, the immune system over-reacts to a substance that is not harmful or disease causing. Commonly, we call this an allergy. – Antibodies are made in large quantities against non-
harmful substances. – Can create local or systemic immune responses including
the inflammatory response, up to a anaphylaxis. – Common allergies include plant pollen, animal dander, and
foods such as peanuts. – We can treat these reaction with medications that block
histamines and other elements of the immune system.
LYMPHATIC SYSTEM
The Lymphatic System
• Series of vessels and nodes throughout the body.
• Functions: – Return fluids to the circulatory system that have
escaped. – Filters fluid for waste and monitors for pathogens. – Helps with absorption of fats/fat soluble vitamins. – Creates Lymphocytes in response to disease.
(Specific immunity)
Lymph Vessels
• These run along the same pathways as the circulatory system. – Fluids in these vessels more very slowly. – Vessles have valves. – Fluid in vessels is called lymph. – Along the lines of lymph vessels, there are lymph
nodes.
Lymph Nodes
• These are oval shapes structures located all through out the body, and especially near the roots of the limbs and in the neck. – If infection is present in the fluid that is filtered in
the node, the immune response begins. – Lymph nodes contain macrophages and create
lymphcytes with help fight disease. – If they become overwhelmed with pathogens,
they will become inflamed.
Tonsils
• Tonsils are like open lymph nodes. – They serve as gate keepers in the respiratory and
digestive tracts. – They catch pathogens and hold them so that they
can be attacked by immune cells. – Research shows that people who have their tonsils
removed due to issues in early life have higher rates of respiratory illness later in life.
Other Lymph Structures
• The Spleen: – Helps to recycle and store red blood cells, as well
as serves to filter blood and make monocytes and lymphocytes,
• Thymus: – Coverts immature lymphocytes to killer T Cells– Most active in early life when immune system is
still developing.
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