Download introduction to the immune system

INTRODUCTION TO THE IMMUNE SYSTEM
For thousands of years people believed that diseases were caused by evil
spirits, magic, evil deeds (sin), and bad air. People who were sick were
often considered cursed, etc.
THE GERM THEORY OF DISEASE- stated that disease is caused by
pathogens (disease causing organisms bacteria, viruses, fungi.....-)-developed by Louis Pasteur and Robert Koch
SOME EXCEPTIONS:
1. Many healthy people carry pathogens but do not exhibit the symptoms of
disease. Typhoid Mary—19th-20th century…..These “carriers” may transmit the
pathogens to others who then may become diseased.
2. Some microbes are very difficult to grow under in-vitro (in the
laboratory) conditions. Examples: viruses, Chlamydia, rickettsias, and bacteria
that cause leprosy and syphilis. Some of the fastidious organisms can now be
grown in cultures of human or animal cells or in small animals-leprosy in
armadillos.
3. Not all laboratory animals are susceptible to all pathogens. Many
pathogens are species specific. Ethical considerations limit the use of
laboratory animals and human volunteers.
4. Certain diseases develop only when an opportunistic pathogen invades a
susceptible host. These secondary invaders or opportunists cause disease only
when a person is ill or recovering from another disease. For example in case of
pneumonia and ear infections following influenza, isolation of bacteria causing
pneumonia may mislead the isolation of influenza virus.
5. Not all diseases are caused by microorganisms. Many diseases are caused
by dietary deficiencies (scurvy, rickets). Some of the diseases are inherited or
are caused by abnormality in chromosomes. Still others such as cancer of the
lungs and skin are influenced by environmental factors.
TYPES OF DISEASES
Infectious Only about 1/2 of diseases
Genetic
Wear and tear
Some prime source of pathogens=contaminated water, soil, food, animals
Transmission may be by
(1) direct contact (common cold)
(2) vectors (malaria, Lyme Disease, Bubonic Plague)
(3) object (food poisoning)
(4) airborne
IMMUNITY is RESISTANCE TO DISEASE
(1) Infectious disease-diseases that can be transmitted by infected animals,
humans, or objects such as contaminated food, water or objects
(2) Contagious disease-narrower-only diseases spread from person to person
Rabies is infectious (from rabid animal bite) but not contagious
Flu is infectious and contagious-spread
Endemic-disease always present in the population-common cold
Epidemic-occurs when many in same area get disease at same time--flu, typhoid
fever, etc.
Pandemic-world wide disease
Treatment (1) Antibiotic bacteria infection= -problem with resistance
(2) Vaccinations-Edward Jenner-=cowpox, smallpox
(3) Interferon-Naturally produced by body to interfere with virus’ ability to
reproduce
(4) Chemotherapy/radiation
A FEW WORDS TO KNOW:
IMMUNITY-specific resistance to disease
PATHOGEN-Disease causing organism
ANTIGEN-substance foreign to the body such as bacteria-elicits immune
response
ANTIBODY-substance that acts against foreign bodies such as bacteria
THERE ARE 2 DEFENSE MECHANISMS
(1) NONSPECIFIC IMMUNITY- not concerned with what type pathogen
or invader attacks the body general defense against anything that the
body recognizes as NOT SELFAdvantage: Meets the enemy as soon as It presents ItselfNEUTROPHILS, MONOCYTES, MACROPHAGES, NK CELLS
(2) SPECIFIC IMMUNITY-mechanisms that recognize SPECIFIC agentsDisadvantage: (1) Must be primed
(2) Takes TIME to recognize their target and react with sufficient force
to overcome the enemy
NONSPECIFIC DEFENSES:
1st Line of Defense:
MECHANICAL BARRIER:SKIN/MUCOUS MEMBRANES/HAIRS/CILIA
CHEMICAL BARRIER:
(a) skin secretions (acid pH)
(b) HCl protects stomach lining/kills bacteria in stomach
(c) saliva and tears contain LYSOZYME, enzyme that
destroys bacteria
(d) sebum-contains bactericide
(e) mucus-sticks pathogens together--sweep away
When nick or cut breaks the surface barriers, microorganisms infiltrate
and then need 2ND LINE OF DEFENSE
2ND LINE OF DEFENSE:NONSPECIFIC DEFENSES---5 PARTS TO THIS
1. INFLAMMATORY RESPONSE-surface barrier is breached by
pathogens or tissues are injured by heat, cold, UV radiation or physical
trauma
INFLAMMATION
Right after injury brief vasoconstriction, then vasodilation SerotoninInhibits neurotransmitters--helps with vasodilation
PUS=mixture of dead or dying neutrophils, broken down tissue cells,
and living and dead pathogens
5 Cardinal Signs of Inflammation
(1) Redness=hyperemia=vasodilation=more blood to area, the chemicals
that promotes this is HISTAMINE
(2) Swelling (edema)=capillaries become more permeable and fluid seeps
out (plasma)
(a) dilutes harmful substances,
(b) brings oxygen and nutrients for repair,
(c) allows clotting proteins in
(3) Pain=caused by swelling pressing on nerve endings
(4) Fever=pyrogens-chemicals causing fever
(5) Impairment of function allows rest and recovery (usually at a joint)
2. PHAGOCYTOSIS
MACROPHAGES AND NEUTROPHILS engulf foreign substances- destroys the substance/pathogen
1st to ARRIVE: MAIN PHAGOCYTE:Neutrophils=ALSO RELEASE into the
surrounding area an oxidizing agent, a chemical (like bleach) which
causes thorough killing activity in the area so that the neutrophils as
well as the pathogen are destroyed
Phagocytes have a short life span and they pile up at the inflammation
site-forming most of the PUS
3. NATURAL KILLER CELLS--NONSPECIFIC
(1) kill cancer and virus infected cells by lysis
(2) attack transplanted tissue/grafts
NKs are a group of LYMPHOCYTES-BUT NOT T OR B (Which ARE
SPECIFIC)
NKs act spontaneously against any virus infected or tumor cellsnonspecific-DAMAGE THE CELL MEMBRANES TO LYSE OR BREAK
THEM APART
4. ANTIMICROBIAL SUBSTANCES
(1) INTERFERON-produced by virus infected cells- binds to other cells
and protects them by interfering with the ability of viruses to
reproduce in these cells
(2) COMPLEMENT-about 20 Inactive enzymes In the plasma
when complement is FIXED AND ACTIVATED chemicals are released
that magnify the inflammatory response-it "complements" the
effectiveness of non-specific and specific response to lyse
microorganisms and enhance phagocytosis and inflammatory response
5. FEVER-370C (98.60F) normal-Part of inflammatory response
Macrophages release pyrogens (chemicals which raise blood
temperature)
HIGH FEVER= Dangerous-inactivates enzymes
MODERATE FEVER=Benefits:
(1) Speeds up metabolism and defensive actions of body
(2) Liver and spleen sequester iron-makes it less available to bacteria
which require a large amount of iron to proliferate
3RD LINE OF DEFENSE: SPECIFIC BODY DEFENSES-IMMUNE
RESPONSE
TO BE SPECIFIC IT MUST RECOGNIZE NOT SELF (UNSELF) AGENTS
These experiments revealed three important aspects of immune
response:
(1) Antigen specific-recognizes and works against particular
antigens-200 different types of strep-different response to each
(2) Systemic-immunity is not restricted to the initial infection siteThe entire body is protected.
(3) Memory-recognizes and mounts a vigorous attack on previously
encountered pathogens.
Thus they discovered 2 TYPES OF SPECIFIC IMMUNITY
(1) ANTIBODY MEDIATED IMMUNITY-provided by the antibodies in the
body fluid--produced by lymphocytes-B CELLS
Antibodies bind to bacteria and their toxins and to free viruses
inactivating them temporarily and marking them for destruction by
phagocytes or complement
(2) CELL-MEDIATED IMMUNITY-provided by NON-ANTIBODY producing
lymphocytes T CELLS
1. directly attack invaders and lyse body cells infected by viruses or
other intracellular parasites, cancer cells,
foreign grafts
2. release chemicals that enhance the inflammatory response or help
to activate lymphocytes or macrophages.
Densest populations of lymphocytes:
1. bone marrow 2. thymus 3. lymph nodes 4. spleen
CELLS OF THE IMMUNE SYSTEM
LYMPHOCYTES:
T or B lymphocyte
INACTIVE B cells-synthesize, but do not secrete antibodies-INSTEAD
they insert about 100,000 antibodies on their plasma membranes- the
combining sites on these antibodies serve as receptors for their
"matching" antigens->leave bone marrow and->lymph nodes, spleen,
other lymphoid tissue
SECOND STAGE-occurs when B cell is activated by an encounter with
its specific antigen-when the epitopes combine with the antibody
combining sites on the surface of the B cell and activate a series of
mitotic divisions--- >>>>CLONE of Identical B cells-->some
DIFFERENTIATE into PLASMA CELLS which produce antibodies--others do not differentiate and are so-called MEMORY B CELLS--which
do not produce antibodies but later if they are exposed to the antigen
that triggered their formation, they will become PLASMA CELLS>antibodies
ULTIMATE FUNCTION OF B CELLS IS TO BE THE ANCESTOR OF
PLASMA CELLS
The antibodies circulate in the blood or lymph where they bind to
antigens and MARK THEM FOR DESTRUCTION BY OTHER SPECIFIC OR
NOT SPECIFIC MECHANISMS