Transcript Immunity (Ag).

Copyright 2010. PEER.tamu.edu
Immunity –
The War Against Infection
 Immunity: ability of an
organism to resist disease.
 Antigen: any substance
that elicits an immune
response.
 Antibodies: made in
response to specific
antigens; can inactivate the
antigen that triggered the
antibody formation.
The Body Fights Back: 2 Ways
 Surface Barriers Keep
Intruders Out
• Prevents entry of antigens inside
our body
• Skin, Mucosa
 Two immune mechanisms:
• Cell Mediated Immunity: Cell
activates itself to defend against the
attack
• Humoral Immunity: Cell produces
antibodies carried in blood to
combat the intrusion
The Invaders
 The Antigen
The Enemy Invader
• Usually a bacteria or
virus
The Warriors
Three Defense Systems:
1. Macrophage cells
2. Lymphocyte (white blood cell)
T cells
3. Lymphocyte (white blood cell)
B cells
The Warriors
 The Macrophage
Body's Radar
 Type of cell normally
present in the blood
 Detects the enemy
and engulfs (eats) it
 This is cell-mediated
immunity.
The Warriors
 The T-Helper Cell
Communication Link
 Communication Link
Between the body's
macrophages and Bcells
This is inactivated in HIV infections!
Macrophage Presents Antigen
to T Cells (white blood cells)
Virus
Virus
Virus
The Warriors
 The B-Cell (white blood cell)
The War Factory
 Produces antibodies custom tailored for
the type of enemy antigen
B-Cells in Action
Virus
Virus
Virus
Virus
Antibodies Need Help
 Antibodies
Antigen Busters
 Designed to seek and
destroy the specific
enemy antigen
 Complement
Support Troops
 Assists the antibodies
to neutralize the
enemy antigen
Antibody Protein & Humoral Immunity
Since antibodies circulate through the body fluids(humours),
the protection afforded by B cells is called humoral immunity.
Structure of
antibodies
(Y-shaped
proteins)
So what does an
antibody do?
1. Binds to molecules
(antigens) on the surface
of invading organism.
2. Inactivates or renders the
microorganism susceptible
to destruction by the
immune system.
ELISA TEST-One Way to Test for Antibodies
• Remove blood cells and use the fluid
(serum) to test for presence of antibody.
• Place target sample on a support.
• Add serum that has antibody against
antigen being tested for. Antibody, if
present, binds the antigen.
• Add a second antibody that was
separately developed to react with the
antibody/antigen complex in step B and
binds it to the complex. Second
antibody was also prepared with an
enzyme attached to it.
• This new complex is made visible by
reacting it with an enzyme that converts
it to a colored compound that you can
see.
Cell-mediated immunity
 It is an immune response that does not involve
antibodies, but rather the cells act as the killers
themselves.
 It protects the body by:
 Activating antigen-specific T-cells that destroy
infected cells.
 Activating macrophages that destroy
intracellular pathogens.
 Activating NK (Natural Killer) cells that release
a protein that kills the target cells
Review 1
 What is the enemy called that invades the
cell?
 What keeps intruders out?
 What are the two kinds of immunity?
Surface Barriers or Mucosal
Immunity
Skin
Cilia
Tears, Saliva, Urine.
Sticky mucus
Stomach:
Hydrochloric Acid
Analogy
 Suppose the classroom is a body.
 All students are cells.
 Rats are Antigens.
 Doors and Windows prevent them from entering
- Surface Barriers.
 Some of you Tough ones (T-cells) will capture
the rodents - Cell-mediated Immunity.
 Some of you Brainiacs (B-cells) will call pest
control (Antibodies) to capture the rodents –
Humoral Immunity.
What do these components look
like?
White Blood Cells:
Other Blood Components:
Source: National Library of Medicine
The Role of Neutrophils
When a wound occurs,
neutrophils migrate out of
blood to rush to the wound
and phagocytize (“eat”) the
bacteria. This is what pus is
made of.
“old” neutrophil surrounded by red
blood cells
The Role of
Monocytes
Eosinophils
Turn into Macrophages
Attack Internal Parasites
Note the notch in the nucleus.
Otherwise, it looks like a
lymphocyte.
Note the red granules
in the cytoplasm.
Role of
Lymphocytes
 They play a major role in defending the host from both
tumors and virally infected cells
 There are two main types of lymphocytes: B cells and T
cells.
 The B cells make antibodies that attack bacteria and
toxins while the T cells attack body cells themselves
when they have been taken over by viruses or have
become cancerous.
 They are often present at sites of chronic inflammation.
The Role of Macrophages
Engulf and then digest cellular debris and
microbes in the body tissues.
Note the irregular cell
membrane. These are
monocytes in the
bloodstream and once they
migrate into the tissues
they become
macrophages.
The Role of Platelets
Blood Clotting
•They can clump
together to form clots.
•No role in immunity.
In this micro-photo of blood cells, platelets are
stained purple. A T-Lymphocyte white cell is
stained green, and a Monocyte white cell is
stained gold. Red blood cells are red.
Stop and Review
 What are the types of white blood cells?
 What is the function of each of the types of
white blood cells?
 What is the role of platelets?
Complete Blood Count (CBC)
 Whether it is a human, dog, cat,
steer, bird or even ferret, when
sick, their doctors typically draw
a blood sample and perform
some tests to help determine a
diagnosis.
 The first test generally used is
the complete blood count
(CBC), which determines the
number and types of blood cells
present.
 This test can provide
information about the status of
the patient’s immune system.
Complete Blood Count (CBC)
 Blood is tested for
several things:
 Red Blood Cells
 White Blood Cells
• Total count and percent
values for each type of
white blood cell
 Platelets
 Other blood components
• hemoglobin
• hematocrit
Click Here for a chart of normal blood values in dogs and cats
Leukocytosis
 Leukocytosis: white blood cell count
increased above the normal range.
 It is not a disorder or a disease, but a
sign of illness.
 It occurs in response to a wide variety of
conditions, including
 viral, bacterial, fungal, or parasitic
infection
 cancer
 Hemorrhage (internal bleeding)
 exposure to certain medications or
chemicals including steroids.
Leukopenia
 Leukopenia: a decrease in the
number of circulating white blood
cells in the blood.
 As white blood cells get “used up”
during infection, leukopenia can
place patients at higher risk for
infection.
 Causes:
 Influenza, typhus, malaria, HIV, tuberculosis,
dengue, Rickettsial infections, enlargement of
the spleen and folate deficiencies.
 chemotherapy, radiation therapy, leukemia ,
myelofibrosis and anemia.
 many common medications like minocyclen.
Immune Disorders in Humans and
Animals:
HIV (Human Immunodeficiency Virus)
 HIV infection in humans causes AIDS (Acquired
Immunodeficiency Syndrome).
 AIDS causes the immune system to fail, leading to life-
threatening opportunistic infections.
 Infection with HIV occurs by the transfer of blood,
semen, vaginal fluid, pre-ejaculate, or breast milk.
 The four major routes of transmission are




unprotected sexual intercourse,
contaminated needles
breast milk
transmission from an infected mother to her baby at birth.
AIDS (Acquired ImmunoDeficiency Syndrome)
 Virus infects vital cells such as helper T cells and
macrophages.
 When T cell numbers decline below a critical level, cell-
mediated immunity is lost, and infections with a variety of
opportunistic microbes appear.
Illustration of the
AIDS virus
penetrating a
white blood cell
and duplicating.
Feline Immunodeficiency Virus
(FIV)
 Similar to HIV, FIV is a condition in cats that is caused by a
virus and causes a reduction in the ability of the immune
system of the cat to fight infection and illness.
 It is sometimes known as Feline AIDS.
 You can't catch AIDs from a cat and a cat can't catch AIDs
from an HIV infected person. This is not a zoonotic disease.
Click here for more information about FIV
See slide note for more resources
FIV continued
 Transmission: Bite wounds from infected cats, especially
during cat fights, rarely by milk or during birth.
 Infected cats may appear normal for years. However,
infection eventually leads to a state of immune deficiency.
The same agents found in the everyday environment--where
they usually do not affect healthy cats--can cause severe
illness in cats with weakened immune systems.
 There is now also a
vaccine to help protect
cats from FIV, however
it does not provide
complete protection.
Cat with Feline Immunodeficiency Virus
Feline Leukemia Virus (FeLV)
 Caused by a virus similar to HIV and FIV.
 Transmitted in the saliva and nasal secretions of infected
cats.
 Also transmitted by urine, feces and milk.
 Unsupervised outdoor cats are most at risk.
 This infection can lead to cancer in cats, blood disorders,
and immunodeficiency which causes cat to be unable to
protect itself against infections.
 There is a vaccine available for FeLV.
Click here for more information on FeLV
Severe Combined Immunodeficiency
Disease in Animals (SCID)
 A recessive genetic disorder that affects Arabian horses. This condition is
fatal, as the animal inevitably succumbs to an opportunistic infection within
the first four to six months of life.
 Carriers, who themselves are not affected by the disease, can be detected
with a DNA test. Careful breeding practices can avoid the risk of an affected
foal being produced.
 Dogs are also known to have SCID. There are two known forms, an X-linked
SCID in Basset Hounds, and a recessive form seen in one line of Jack
Russell Terriers that is similar to SCID in Arabian horses.
Review 3
 What is a CBC?
 What is Leukopenia and what are its
causes?
 What is Leukocytosis and what could it be
an indicator of?
 Name four immune disorders and tell what
causes them and what species they affect