Download immune response

immunity
by : Dr Samia Sadig Moh.
Host defence
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Nonspecific Defenses
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There are several categories of nonspecific
defenses:
Physical barriers: skin & mucus membranes.
Secretions.
Phagocytes?
Interferons
Complement
Inflammatory response
Fever
Normal flora.
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Skin
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Most imp barrier. Epidermal epithelium
has multiple layers of dead, keratinized
cells and a network of desmosomes
locking the cells together.
Can't be penetrated by most organisms
unless there is a ?.
pH (< 7.0) of skin secretions inhibits
bacterial growth
Hair follicles secrete sebum that contains
lactic acid and fatty acids both of which
inhibit the growth of some pathogenic
bacteria and fungi  Areas of the skin
not covered with hair, such as ? are most
susceptible to fungal infections
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The epithelia linings
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In the digestive, respiratory,
reproductive, and urinary tracts .
Coughing, sneezing& vomiting?
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Secretions
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The stomach contains a very low pH and
proteases that can destroy pathogens.
Urine flushes the urinary tract while
glandular secretions flush the
reproductive tract.
Saliva, tears, nasal secretions, and
perspiration contain lysozyme which
damage or kill bacteria.
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The innate immune responses
Involves :
 Phagocytic cells (neutrophils, monocytes, and
macrophages).
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Cells that release inflammatory mediators
(basophils, mast cells, and eosinophils);
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Natural killer cells (NK cells).
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Molecules such as complement proteins, and
interferon.
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Complement
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A set of proteins
circulating in plasma.
Synthesized by the liver.
Complement can be
activated by interacting
with sugars on a
bacterium's surface or by
interacting with an antigenantibody complex.
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Complement
Direct lyses
Opsonization
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Inflammation
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A localized tissue response to
injury that results in:
pain, redness, swelling, and
heat.
The goals of inflammation
are:
-Prevent additional pathogen
entry.
-Slow the spread of
pathogens away from the
area.
-Mobilize defenses that can
overcome the pathogens
- Facilitate permanent repair.
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Fever
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Bacterial toxins, antigen-antibody complexes,
and interleukin-1 (a chemical released by
active macrophages) all act as pyrogens.
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Pyrogens reset the body's thermostat and
cause a rise in temperature.
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The rise in temperature causes an increase in
the body's metabolic rate which allows the
WBCs to function with greater efficiency.
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Acquired (Specific) immune
response
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Humoral immunity= B- Lymphocytes:
Responds to bacteria, parasites, and any
extra cellular organism.
Cell mediated immunity= T-Lymphocytes.
Responds to viruses, intracellular
organism, malignant cells, transplanted
tissues.
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Classification into T & BLymphocytes
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Acquired immune response
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Presentation of foreign
antigens
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Macrophages phagocytose an organism
partially or completely 
Present some of the organism antigens on its
surface 
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Lymphocytes recognize the presented antigens
as foreign and respond to it.
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Antigen
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Antigens are
macromolecules that
elicit an immune
response in the body.
Antigens can be :
-proteins
-polysaccharides
Rarely:
-lipoproteins
- glycolipids.
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Acquired immune response
Acquired immunity exhibits several
important properties:
1-Specificity.
2- Clonal selection.
3-Memory.
4- Tolerance of self antigens.
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1-Specificity
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T cells and B cells respond to
the molecular structure of the
antigen.
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The antigen's shape/size will
determine which lymphocytes
will respond to its presence..
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Each T cell and B cell has
specific receptors that will bind
to one specific antigen, ignoring
all others.
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Clonal selection
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T and B cells in the human body includes millions of
different lymphocyte populations. Each population
consists of several thousand cells with receptors in
their membranes that differ from those of other
lymphocyte populations.
Each group of lymphocytes will respond to a
different antigen. When antigen exposure occurs, a
lymphocyte specific for that antigen will divide,
producing more lymphocytes with the same
specificity.
This division results in the production of an army of
cells (known as clones) that will deal with the
particular antigen.
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Memory:
1ry & 2ndry response
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First contact with a
foreign antigen 
production of
memory T and B
lymphocytes.
If the same antigen is
encountered again ,
memory cells
response is faster
and stronger.
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4-Tolerance
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During their differentiation in the bone
marrow (B cells) and thymus (T cells), cells
that react to antigens normally present in
the body are destroyed.
Thus, mature T and B cells will ignore
normal self-antigens and attack only foreign
non-self antigens.
Abnormalities in this process autoimmune
diseases : ?
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Cell Mediated Immunity
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Cell Mediated Immunity
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Cytotoxic T-cells are
antigen specific
NK cells are
destroyany abnormal
body cells, e.g., tumor
cells or cells infected
by a virus i.e non specific
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Humoral Immunity
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Ag-Antibody reactions
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Active immunization
Vaccination
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A weak or dead organism
(antigen) is introduced into
the body.
The immune system imitates
a 1ry response and produces
memory cells.
If the person is exposed to
the real disease , the immune
system responds by a 2ndry
response which is?
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Passive immunization
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The subject is injected with serum
containing ready made antibodies formed
by another animal exposed to the
antigen.
Examples : snake’s anti-toxin, anti-rabies,
anti-tetanus serum.
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Allergies
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Allergies are excessive and inappropriate
responses to (typically) harmless
antigens, such as the pollen.
Examples : bronchial asthma, hay fever.
contact dermatitis
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Auto-immune diseases
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The immune system usually distinguishes "self"
from "non-self".
Autoimmune diseases result when the immune
system attacks and destroys cells and tissues of
the body.
Juvenile diabetes, Grave's disease, Multiple
sclerosis, Systemic lupus erythematosus, and
Rheumatoid arthritis are some of the
autoimmune diseases.
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Thank You
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