Transcript Immune Response

Immune Response
Vocabulary
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Immunology- the study of host defense mechanisms
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Immunity- ability of the host to protect itself against foreign
organisms. Resistance to disease.
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Antigen (Ag)- is a foreign substance that can elicit specific
immune response (IR) when is immunogenic
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Antibody (Ab)- protein produced by the body’s immune
system when it detects harmful substances called antigens
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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
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Neutrophils
Eosonophils
Basophils
Lymphocytes (T and B Cells)
Monocytes
Divided into two categories
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Granuolocytes and Agranuolocytes
Granuolocytes
Neutrophils
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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
Granuolocytes
Eosonophils
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Function in phagocytosis
Account for less than 5% of
WBC
Increased # often present
in patients with parasitic
infections or allergies
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Basophils
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Rarest WBC in blood
Non phagocytic
Function as “sirens” for
inflammation and allergy
Agranuolocytes
Lymphocytes
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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
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T cells and B cells, which differ in function and the molecules that are
on their surface also differs
Agranuolocytes
Lymphocytes
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T cells
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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
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“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
Agranuolocytes
Lymphocytes
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B cells
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Circulate in the blood in an immature way
About 10% that circulate the blood are B cells
Produce proteins known as antibodies
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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
Agranuolocytes
Monocytes
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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
The Immune System
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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.”
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“Non-self” entities include:
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Microorganisms, transplants, tumors, foreign substances (eg:
asbestos, particulate matter)
The Immune Response
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Natural or Innate Immunity (IIR)
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Non-specific
Acquired or Adaptive Immunity (AIR)
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Specific
The Immune Response
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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
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It makes it possible that although we spend our lives
surrounded by germs, we sporadically get sick.
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Most infections are fixed successfully by IIR, other that IIR can
not resolve, AIR is triggered and overcome successfully,
followed by lasting immunological memory
Innate Immune Response (IIR)
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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
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First line of defense against pathogenic “invaders”
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Skin
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Mucus
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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
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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
Washing actions of tears, saliva, and urine removes bacteria and foreign
particles from the body
Natural or Innate Immunity: Inflammation
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When pathogenic agents penetrate external barriers, the
first reaction of the body is the inflammatory response
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Any time the cells or tissues of the body are injured,
internally or on the surface, by whatever agent, the
inflammatory response occurs
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Acute Inflammatory Response (AIR)- occurs in blood vessels
near injury
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AIR helps leukocytes to leave the blood vessel (diapedesis or
emigration) & travel to injury site via chemotaxis
Acute Inflammatory Response
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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)
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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
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Complement- a complex of interrelated and interacting
proteins manufactured in the liver
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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
Phagocytosis
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Adaptive or Acquired Immune Response
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Everyone is born with natural immunity to disease, but
we can also acquire immunity to disease
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Acquired immunity can be acquired naturally or artificially,
and it can be active or passive
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Acquired or Adaptive Immune Response
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Refers to antigen specific defense mechanisms that take
several days to become protective and are designed to
react with and remove specific antigens
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This immunity is developed throughout life
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Acquired or Adaptive Immune Response
There are two major branches of the adaptive immune
response
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Humoral
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Antibody- mediated
immune response
Mediated by B-lymphocytes
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Cellular
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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
Acquired or Adaptive Immune Response
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During adaptive immunity:
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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
Antigen Processing and Presentation
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In order to generate adaptive immunity, as well as long
lasting memory, Ag should be recognized by T and B cells
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Memory usually improves upon repeated exposure to a given
infection
Acquired Immunity
Type of Immunity
How acquired by Host
Examples
Active Natural Immunity:
Antibodies are produced by the host in
response to the infectious agent itself
(e.g. Recovery from disease)
Active Immunity
Passive Immunity
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Occurs when an individual is exposed
to an infectious agent or one of its
products (antigens)
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
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 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
Differences in Innate and Adaptive
Immunity
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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
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(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
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(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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