Transcript Unit Three

Unit Two
Immune System
Pathogens Cause Disease
• It is important to understand people become
ill due to two main reasons:
– Improper function of internal organs etc.
– Infection caused by pathogen
*** With proper preventative care, the incidence of
infections caused by pathogens are minimal
What are Pathogens
• Pathogens are microorganisms that invade the
human body (other species also). They cause
damage to internal organ structure and the
proper function of organs
• There are three types of Pathogens:
– Bacteria
– Viruses
– Prions
Bacteria
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Prokaryotic
DNA and Ribosomes only
Cell Wall surrounds Plasma Membrane
Obtain nutrients from a variety of sources
including a “Host’s” cells
• Shape is that of a Sphere, Rod, or Spiral
• Most are harmless, and some are beneficial to
digestion (think yogurt)
Viruses
• Smaller than Bacteria
• Their structure consists of RNA/DNA
surrounded by a Protein Coat protective layer
• Are not considered living because they cannot
replicate themselves without a “Host”
• In order to replicate they must insert their
genetic material (RNA/DNA) into the DNA of a
Host’s cell….. This can spread to billions of the
Host’s cells eventually causing death
Prions
• They are ill-formed brain cell proteins that infect
and subsequently change the shape of other
healthy brain cell proteins
• Eventually the brain ceases to function due to all
the ill-formed proteins
• “Mad Cow Disease” is a Prion disease that first
appeared in cows, then spread to the human
population (mainly in Great Britain)
• Not as common as viral and bacterial infections
Pathogen Success
• There are three factors that determine the
evolutionary success of a pathogen:
– Ease of Transmission
– Mode of Transmission
– Virulence
Human Body’s Defense
• The body’s immune system responds to
pathogens/allergens with three levels of action:
– Physical and Chemical Barriers
• Skin, Hair, Mucus, Stomach Acid etc.
– Innate /Nonspecific Response
• Phagocyte action
– Acquired/Specific Response
• Lymphocyte action (B and T cells)
Physical & Chemical Barriers
• Skin – solid physical barrier that is acidic and constantly
replaced
• Tears – expels foreign contaminants
• Earwax – prevents contaminants from gaining access to
the ear canal
• Mucus – similar function as that of tears and earwax
• Vomiting – expels contents from stomach that may
have pathogens
• Urination/Defecation – expels waste material possibly
contaminated with pathogens from body
Innate/Nonspecific Response
• If the pathogen is able to breach the external
physical and chemical barriers now the body
must actively seek out the intruder and destroy it
• Also, after the pathogen is destroyed, the body
must repair the damage done to it by the
pathogen
• Nonspecific Defense Mechanisms respond to all
types of health challenges, including pathogen
infections
Innate/Nonspecific
• Phagocytes – Neutrophils (1st responders) and
Macrophages engulf and digest foreign cells;
Eosinophils cluster around large parasites & excreting
digestive enzymes to kill them
• Natural Killer Cells – release chemicals that disintegrate
cell membranes of tumor cells and virus-infected cells
• Inflammatory Response – redness, warmth, swelling,
and pain attract Phagocytes & promotes tissue healing
• Interferons – stimulate the production of proteins that
interfere with viral production
• Fever – mid-grade fevers make environment less
welcoming to pathogens
Phagocytotic Process
Acquired/Specific Response
• Lymphatic System is responsible for three bodily
functions:
– defend the body against infection and injury
– Maintain volume of blood in circulatory system
– Transports fats and vitamins from digestive to
circulatory system
Lymphatic System
Lymph Nodes
• Lymph nodes are small organs in the Lymphatic
System,
• Located in the neck, armpit, and groin.
• They remove microorganisms, cellular debris, and
abnormal cells from the “Lymph” (milky fluid) before
returning it to the Circulatory System (aka
Cardiovascular System)
• Recall Lymph comes from the portion of the blood
plasma that diffuses out of the capillaries
Spleen
• One of the Spleen’s primary function’s is to
fight infection
• “Red Pulp” in the Spleen contains
“Macrophages” that scavenge and destroy
microorganisms, old/damaged red blood cells
and platelets
• The Spleen cleanses the blood (Red Pulp) and
the Lymph Nodes cleanse the Lymph (Milky
Fluid)
Immune System and Antigens
• An Antigen is a marker placed on a pathogen to
identify it as a foreign invader; it causes an Immune
Response
• Lymphatic System responds by producing B and T
cells
• The B cells produce 5 types of Antibodies (GAME D)
that sequester the Antigen marked Pathogen
• The T cells then arrive to dispose of the Pathogen
Lymphocytes
• Lymphocytes play key role in the innate/specific defense
mechanism
• 2 types of Lymphocytes:
– B lymphocytes
• B cells mature in bone marrow
• Responsible for antibody mediated immunity; focus on
removing antigens from blood and lymph
– T lymphocytes
• T cells mature in thymus gland
• Responsible for cell mediated immunity; focus on
destroying infected cells
B Cells
• Responsible for antibody-mediated immunity
• B cells produce antibodies – proteins that bind with
and neutralize specific antigens
• Often referred to as “Immunoglobulins”
• B cells work best against viruses, bacteria, and
foreign molecules that are soluble in blood and
lymph
• B cells mature in bone marrow, then travel via
circulatory system to lymph nodes, spleen, and
tonsils where they remain inactive until needed
B Cells
• When B cells become active, they reproduce
additional cells to fight the antigen
• Those new cells are called Clones/Plasma Cells
• Some of the Clone Cells become Memory Cells –
long lived cells that “remember” that initial
antigen and can reactivate to attack it again if
needed
• Memory Cells store information about the
pathogen, and as a result, the immune response
is much quicker the second time infection occurs
5 Classes of Antibodies
T Cells
• Responsible for cell-mediated immunity
• T Cells do not produce antibodies
• Some T Cells directly attack foreign cells that
carry antigens
• Most T Cells release proteins that help coordinate
the immune response: actions of T Cells, B Cells,
and Macrophages
• Cell mediated immunity protects the body against
parasites, bacteria, viruses, fungi, cancer cells,
and cells perceived as foreign (tissue rejection)
T Cells
• T Cells responsible for cell-mediated immunity
develop from stem cells in bone marrow
• T Cells mature in Thymus Gland
• T Cells react to fragments of antigens, not the
whole antigen
T Cells
• Types of T Cells include:
– Helper T Cells: direct/enhance activities of many
cell types in the Immune System
– Cytotoxic T Cells: attack and destroy abnormal
cells
– Memory T Cells: reactivate upon later exposure to
same antigen to form Helper and Cytotoxic T Cells
– Suppressor T Cells: may suppress immune
response after an antigen has been destroyed
Immune System Facts
• Immunity – body does not suffer the effects of the
pathogen as a result of Memory Cells facilitating a
Secondary Immune Response that is quick and decisive
• Immunization – injection of monoclonal antibodies and
antibiotics into the body to assist with the immune
response
• Vaccine – an “active immunization” which involves the
injection of weakened antigens into the body with the
intent of enabling the body to produce Memory Cells
to fight the pathogen if it reenters the body in a
healthy state (secondary immune response)
Immune System Facts
• Active Immunity develops after a primary
immune response which is a response to
exposure to a live pathogen and development
of symptoms. The cells produce the antibodies
themselves. (see vaccine)
Passive Immunity is when a person's cells do
not produce the antibodies, they receive them
by an injection of antibodies or antitoxin.
Immune System Facts
• Monoclonal Antibodies – produced in a lab from
cloned descendants of a single hybrid B Cell
• Antibiotics – drugs that kill or inhibit growth of
bacteria; when discovered were derived naturally,
now are synthesized in a lab
• Allergy – inappropriately strong response of the
Immune System to an allergen
• Allergen – any substance that causes an adverse
bodily reaction
HIV/AIDS
• History
– First documented in January of 1981 by the Center
for Disease Control
– Thought to have spread to the USA by a gay flight
attendant who traveled abroad
– Originally called the “Gay Cancer” and/or “Gay
Plague” because the initial outbreak was mainly
confined to homosexual males
HIV/AIDS
• History continued
– Less than a year later the list of at risk individuals
expanded to include intravenous drug users,
recent Haitian immigrants, and Hemophiliacs
regardless of sexual orientation
– The virus that causes AIDS was first discovered by
a French scientist in 1983
– Circa 1987, Rock Hudson announced he had AIDS
and died shortly after
HIV/AIDS
• History continued
– In the 1990’s heterosexual celebrities and professional
athletes announced they too had acquired HIV: Magic
Johnson and Arthur Ashe
– The 1990’s saw large amounts of research dedicated to
treatment drugs and finding a cure
– Currently there are some very effective drugs to treat HIV
and keep it from developing into AIDS
– Majority of new cases are in Sub-Saharan Africa, and
unfortunately those people lack the finances to pay for
those drugs to treat HIV
HIV/AIDS
• Three phases of the disease
– Acute Phase
• Virus infects person (host) and replicates ferociously
• Replication process causes death of lymphocytes in the person’s
blood
• Person may be asymptomatic for several weeks; if person does
have symptoms they include fever, chills, aches, swollen lymph
nodes, and an itchy rash
• After many weeks the person’s body reacts to the foreign invader
by producing numerous immune cells to fight the virus
• HIV virus targets Helper T Cells by using that cell’s DNA to replicate
its genetic information (RNA) to produce many more viruses
HIV/AIDS
– Chronic Phase
• Several months to several years an untreated individual
will most likely progress to this phase
• The continued replication of viruses in the host T Cells
leads to the body’s inability to fight off common
infections because the Immune System is essentially
destroyed
• Number of HIV viruses increases causing reemergence
of symptoms like fatigue, persistent fever, night sweats,
persistent cough, and persistent diarrhea
• These symptoms are a signal that full blown AIDS will
develop soon
HIV/AIDS
– AIDS
• Lymphocyte count has dropped drastically; viruses have
taken over the blood
• Person is extremely weak and thin due to persistent
diarrhea and coughing
• Person eventually dies due to the presence of another
infection
• People do not die from AIDS, but rather, Acquired
Immune Deficiency Syndrome weakens their bodies
ability to fight other common infections
*** There is currently no cure for HIV/AIDS
HIV/AIDS
• In 2010, people can live for many years with HIV/AIDS due
to the presence of drugs that keep the replication process
to a minimum
• If you are poor, and especially if you live in a less developed
nation, you may not have access to these powerful drugs
• AIDS is deadly; the best course of action is to not be
exposed to the virus
• It is worth noting, the method that is 100% effective at
preventing exposure to AIDS and other STD’s is Abstinence
• Update 7/8/2010:
http://www.foxnews.com/story/0,2933,596242,00.html?te
st=latestnews