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Immune Response
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Vocabulary Immunology- the study of host defense mechanisms
Immunity- ability of the host to protect itself against foreign organisms. Resistance to disease.
Antigen (Ag)- is a foreign substance that can elicit specific immune response (IR) when is immunogenic
Antibody (Ab)- protein produced by the body’s immune system when it detects harmful substances called antigens
White blood cells (leukocytes)- chief function is to protect the body against microorganisms causing disease and fight infection when it occurs. They are bigger than red blood cells.
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White Blood Cells (WBC) 5 Major types of WBC
Neutrophils Eosonophils Basophils Lymphocytes (T and B Cells) Monocytes
Divided into two categories Granuolocytes and Agranuolocytes
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Granuolocytes Neutrophils
are the most common WBC in peripheral blood. Circulate in blood 7-10 hrs before migrating into
tissue Live only a few days “front line of innate defense” Increased # used as an indicator of infection Extravasate in inflammation rxn Active phagocytes
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Granuolocytes Eosonophils
Function in phagocytosis
Account for less than 5% of WBC
Increased # often present in patients with parasitic infections or allergies
Basophils Rarest WBC in blood Non phagocytic Function as “sirens”
for inflammation and allergy
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Agranuolocytes Lymphocytes
Cornerstone of the immune system Much smaller than the 3 granuolocytes Help provide a specific response to attack the
invading organisms Are formed in lymphatic tissue throughout the
body Two types of lymphocytes
T cells and B cells, which differ in function and the molecules that are on their surface also differs
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Agranuolocytes Lymphocytes
T cells Circulate through they thymus gland and have turned
into cells known as thymocytes When exposed to antigens, they rapidly divide and
produce large number of new T cells that are sensitive to that type of antigen
More than 80% of lymphocytes circulating in the body are T cells
Divided into 2 main groups “killer cells” because they produce chemical substances
that are essential in helping the B cells destroy foreign substances
Helper T cells which assist the “killer cells” in performing their activities and help protect the body against diseases in other ways
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Agranuolocytes Lymphocytes
B cells Circulate in the blood in an immature way About 10% that circulate the blood are B cells Produce proteins known as antibodies
Antibodies attach to foreign pathogens in the body known as antigens that are found on the surface of certain microorganisms
When B cells divide they produce an identical copies of antibodies on their surface
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Agranuolocytes Monocytes
Largest WBC found in the blood Originate in the bone marrow Play important role in the inflammatory response Present pieces of pathogens to T cells so that
pathogens may be recognized and killed Leave the blood stream to become macrophages As a monocyte or macrophage, these cells are
phagocytic (engulfing) and defend the body against viruses and bacteria
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The Immune System The immune system is a group of cells &
soluble molecules, which interact & distinguish patterns in the body as “self” or “non-self,” in order to eliminate those that are “non-self.”
“Non-self” entities include: Microorganisms, transplants, tumors, foreign
substances (eg: asbestos, particulate matter)
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The Immune Response Natural or Innate Immunity (IIR)
Non-specific
Acquired or Adaptive Immunity (AIR) Specific
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The Immune Response To achieve its duty, the immune system has
developed two mechanisms: innate immune response (IIR) & adaptive immune response (AIR). Together, these two systems provide an efficient defense system
It makes it possible that although we spend our lives surrounded by germs, we sporadically get sick. Most infections are fixed successfully by IIR, other
that IIR can not resolve, AIR is triggered and overcome successfully, followed by lasting immunological memory
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Innate Immune Response (IIR) Is the first line of defense in the Immune
response Crucial to control of microorganisms growing
freely during early stage of IR Lacks memory It is not antigen (Ag) specific There are a limited recognition molecules Leads to the AIR
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IIR: External Barriers First line of defense against pathogenic “invaders”
Skin Largest organ in the body Produce lactic (low pH) & fatty acids, sweat, skin oils, which
make it difficult for microorganisms (MO’s) to survive When skin is injured, protects the body by way of inflammation
Mucus Mucosal membranes (mb) lining inner surfaces of the body
secrete mucus, which function as protective carbohydrate layer to stop bacterial invasion
Also traps and removes bacteria & particulate matter, by complementary action of cilliary movement, sneezing, coughing
Body secretions Washing actions of tears, saliva, and urine removes bacteria
and foreign particles from the body
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Natural or Innate Immunity: Inflammation When pathogenic agents penetrate external
barriers, the first reaction of the body is the inflammatory response
Any time the cells or tissues of the body are injured, internally or on the surface, by whatever agent, the inflammatory response occurs Acute Inflammatory Response (AIR)- occurs in
blood vessels near injury AIR helps leukocytes to leave the blood vessel
(diapedesis or emigration) & travel to injury site via chemotaxis
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Acute Inflammatory Response Chemotaxis- is the movement of cells in
response to a chemical attractant In the inflammatory response, chemicals called
mediators, lure the leukocytes to the inflammatory site, where they release enzymes and begin the process of phagocytosis (engulfing and destroying foreign particles or organisms) Histamine was the first chemical identified as a mediator
of the inflammatory response Interferon- if the cell injury is due to viral
infections, interferon, a protein that protects the body against viral infections is released
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Acute Inflammatory Response Complement- a complex of interrelated and
interacting proteins manufactured in the liver Active in inflammation and phagocytosis and also
assists the action of antibodies in the specific response in the infecting agent is not destroyed by the nonspecific defenses
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Phagocytosis
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Adaptive or Acquired Immune Response
Everyone is born with natural immunity to disease, but we can also acquire immunity to disease
Acquired immunity can be acquired naturally or artificially, and it can be active or passive
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Acquired or Adaptive Immune Response
Refers to antigen specific defense mechanisms that take several days to become protective and are designed to react with and remove specific antigens
This immunity is developed throughout life
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Acquired or Adaptive Immune ResponseThere are two major branches of the adaptive immune response
Humoral Antibody- mediated
immune response Mediated by B-
lymphocytes
Cellular Cell-mediated
immune response Involves the
production of cytotoxic T- lymphocytes, activated macrophages, activated NK cells, and cytokines in response to an antigen
Mediated by T-lymphocytes
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Acquired or Adaptive Immune Response During adaptive immunity:
Bone marrow & thymus (primary lymphoid tissues) produce B cells and T cells, respectively
Immature T cells migrate to thymus and become competent T cells
B cells and T cells recirculate through spleen and lymph nodes (secondary lymphoid tissues)
Antigen (Ag) presenting cells (APC) pick up antigen and migrate to secondary lymphoid tissues & interact with T cells and B cells
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Antigen Processing and Presentation In order to generate adaptive immunity, as
well as long lasting memory, Ag should be recognized by T and B cells Memory usually improves upon repeated exposure
to a given infection
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Acquired ImmunityType of Immunity How acquired by Host Examples
Active Immunity Occurs when an individual is exposed to an infectious agent or one of its products (antigens)
Active Natural Immunity: Antibodies are produced by the host in response to the infectious agent itself (e.g. Recovery from disease)
Active Artificial Immunity: Occurs through vaccination with a form of the disease microorganism. It may be dead, attenuated (weakened), or altered so that it will not produce the disease but will cause the body to produce antibodies.
Passive Immunity
As a result of acquisition of antibodies which have been produced by another animal (by active means) or derived from cells grown in tissue culture
Passive Natural Immunity: Transfer of antibodies from a mother to her baby through the placenta; Transfer of antibodies from mother to infant in milk if nursing.
Passive Artificial Immunity: Acquired through inoculation with antibodies. Injection of immune serum from an individual previously immunized or recovered from disease
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Differences in Innate and Adaptive Immunity The innate and adaptive immune responses both
function to protect against invading organisms, but they differ in a number of ways
(1) The innate immune system is constitutively present and reacts immediately to infection. The adaptive immune response to an invading organism takes some time to develop
(2) The innate immune system is not specific in its response and reacts equally well to a variety of organisms, whereas the adaptive immune system is antigen-specific and reacts only with the organism that induced the response
(3) The adaptive immune system exhibits immunological memory. It "remembers" that it has encountered an invading organism (antigen) and reacts more rapidly on subsequent exposure to the same organism. The innate immune system does not possess a memory.
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