Download Plants, Invertebrates, and Vertebrates have multiple nonspecific

Plants, Invertebrates, and Vertebrates have
multiple nonspecific immune response
mechanisms, but….
Lack the pathogen-specific immune responses
seen in mammals
In Innate (non specific) immunity, recognition
and response rely on shared pathogen traits
-Innate immune responses include barrier
defenses as well as defenses to combat any
pathogens that enter the body
Barrier Defenses
-Include skin and the mucous membranes that
cover the surface and line the openings of the
animal body
-These provide a physical barrier to pathogens,
produce secretions that result in a skin pH from 2
to 5, and produce the antimicrobial protein
lysozyme found in saliva, mucous secretions, and
tears (breaks down the cell walls of bacteria)
Cellular Innate Defenses
-Combat pathogens that get through the barrier
defenses- for example, in a cut. They include
phagocytic white blood cells (leukocytes) and
antimicrobial proteins.
A Local Inflammatory Response
Natural Killer Cells
Cellular Innate (non specific) Responses:
Phagocytic White Blood Cells
Cellular Innate (non specific) Responses:
Antimicrobial Proteins
-A local inflammatory response is triggered by
damage to tissue by physical injury or the entry
of pathogens
-It leads to the release of numerous protein
chemical signals
-For example, histamines are released in
response to injury
-Histamines trigger the dilation and permeability
of nearby capillaries. This aids in delivering
clotting agents and phagocytic cells to the
injured area
-Natural killer (NK) cells are WBCs that help
recognize and remove pathogen infected cells
with damaged cell receptors by binding to them
and releasing toxins into them.
-Neutrophils are smaller white blood cells that
ingest and destroy microbes in a process called
phagocytosis.
-Monocytes are another type of phagocytic
leukocyte found in the blood. When they migrate
into tissues, they develop into macrophages,
which are giant phagocytic cells that can attack
larger pathogens and tumor cells.
-Eosinophils are leukocytes that defend against
parasitic invaders such as worms, by positioning
themselves near the parasite’s wall and
discharging hydrolytic enzymes.
-Interferon proteins provide innate defense
against cells invaded by viruses. These are
secreted by infected cells and stimulate
neighboring cells to produce proteins that help
them defend against the viruses.
-The complement system is a group of about
twenty proteins that “complement” defense
reactions. These proteins help attract phagocytes
to foreign cells and help destroy foreign cells by
promoting cell lysis .
Acquired (specific) Immunity: Vertebrates have
two types of Lymphocytes
-Vertebrates have two types of lymphocytes: B
lymphocytes (B cells), which proliferate and
mature in the bone marrow, and T lymphocytes
(T cells), which are made in the bone marrow but
mature in the thymus
-They circulate through the blood and lymph,
and both recognize particular (specific) microbes
Antigens
-Are foreign molecules that elicit a response by
lymphocytes
-B and T cells recognize them by specific
receptors imbedded in their plasma membrane
Antibodies
-Are soluble proteins secreted by B cells during
an immune response that bind to antigens
B- or T- cell activation occurs when an antigen
binds to a B or T cell
-B-cell activation is enhanced by proteins called
cytokines. The B-cells then form two types of
cells called plasma and memory cells.
-This results in a thousands of B cells with
antibodies, all specific to this antigen
-Plasma cells are B cells that produce their
specific antibodies which then circulate through
the body, binding to antigens
-Memory cells, are B cells which are long-lived,
bear receptors for the same antigen and
circulate in the body to quickly mount an
immune response in later infections
B- Or T- cell Continued…
Specificity of B and T cells
-B-cell receptors, or antibodies, bind to antigens
on the surface of an invading pathogen,
inactivating them. Inactivation is followed by
macrophage phagocytosis.
-T-cell receptors then bind antigens that are
displayed by antigen-presenting cells (like
macrophages) on their surface.
(Like B cells, the plasma membranes of T cells
have antigen receptors. However, these
receptors are not antibodies, but recognition
sites for molecules displayed by nonself cells.)
-The specificity of B and T cells is a result of the
recombination of several gene segments in their
DNA that control the shape of their receptor
sites and results in more than 1 million different
B cells and 10 million different T cells.
-Each B or T cell responds to only one specific
type of antigen
Two Branches of Acquired (specific) Immunity
-Humoral immune response involves the
activation of memory and plasma B cells, which
produce antibodies that circulate in the blood
and bind to antigens
-Cell-mediated immune response involves the
activation of cytotoxic T cells, which identify and
destroy infected cells
Defending Against Infection
-Helper T cells aid both responses. When
activated by binding to an anitgen presenting cell
they secrete cytokines called interleukins that
simulate and activate both B cells and cytotoxic T
cells
Organize Your Thoughts On Immunity Names
-B cells make antibodies, which provide humoral
immunity. This helps fight pathogens that are
circulating in the blood
-Cytotoxic T cells destroy body cells that are
infected by a pathogen or cancer cells.
-Helper T cells activate both B and T cells
Destroying the Antigen
-Recall that activated B cells produce memory
cells as well as plasma cells. The plasma cells
fight the initial pathogens and secrete antibodies
in huge numbers during the primary immune
response
-These antibodies will circulate in the blood, and
bind the antigen if encountered again later
during the secondary immune response
Destroying the Antigen: Primary and Secondary
-A primary immune response occurs when the
body is first exposed to an antigen and a B or T
lymphocyte is activated
-A secondary immune response occurs when the
same antigen is encountered at a later time. It is
faster and of greater magnitude
Immunity
-Active immunity develops naturally in response
to an infection; it also develops artificially by
immunization (vaccination). In immunization, a
nonpathogenic form of a microbe of part of a
microbe elicits an immune response resulting in
immunological memory for that microbe.
-Passive immunity occurs when an individual
receives antibodies, such as those passed to the
fetus across the placenta and to infants via milk.
HIV and the Immune System
-HIV viruses infect helper T cells. Can you see
why people with AIDS are immune suppressed?
-Note what cell is central in both humoral and
cell-mediated immunity
Autoimmune Diseases
-Lupus, rheumatoid arthritis, and multiple
sclerosis are examples of autoimmune diseases
-In each case, the immune system turns against
particular molecules of the body, generating
antibodies that attack and damage the body’s
own healthy cells