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Immunity –Immunity –The War Against InfectionThe War Against Infection

Immunity: Immunity: ability of an ability of an organism to resist disease.organism to resist disease.

Antigen:Antigen: any substance any substance that elicits an immune that elicits an immune response. response.

Antibodies:Antibodies: made in made in response to specific response to specific antigens; can inactivate the antigens; can inactivate the antigen that triggered the antigen that triggered the antibody formation.antibody formation.

The Body Fights Back: 2 WaysThe Body Fights Back: 2 Ways

Surface Barriers Keep Surface Barriers Keep Intruders OutIntruders Out• Prevents entry of antigens inside Prevents entry of antigens inside

our bodyour body• Skin, MucosaSkin, Mucosa

Two immune mechanisms:Two immune mechanisms:• Cell MediatedCell Mediated Immunity: Cell Immunity: Cell

activates itself to defend against the activates itself to defend against the attackattack

• HumoralHumoral Immunity: Cell produces Immunity: Cell produces antibodies carried in blood to antibodies carried in blood to combat the intrusioncombat the intrusion

The InvadersThe Invaders

The AntigenThe Enemy Invader

• Usually a bacteria or virus

The Warriors

Three Defense Systems:Three Defense Systems:

1.1.Macrophage cellsMacrophage cells

2.2.Lymphocyte (white blood cell) T Lymphocyte (white blood cell) T cellscells

3.3.Lymphocyte (white blood cell) B Lymphocyte (white blood cell) B cellscells

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 WarriorsThe Warriors

The Warriors

The T-Helper CellCommunication Link

Communication Link Between the body's macrophages and B-cells

This is inactivated in HIV infections!

Macrophage Presents Antigen Macrophage Presents Antigen to T Cells (white blood cells)to T Cells (white blood cells)

Virus

Virus

Virus

The B-Cell (white blood cell)The War FactoryProduces antibodies custom tailored for

the type of enemy antigen

The Warriors

B-Cells in ActionB-Cells in Action

Virus

Virus

Virus

Virus

AntibodiesAntigen BustersDesigned to seek and

destroy the specific enemy antigen

Antibodies Need Help

ComplementSupport Troops Assists the

antibodies to neutralize the enemy antigen

Antibody Protein & Humoral ImmunityAntibody Protein & Humoral Immunity

Since antibodies circulate through the body fluids(humours), Since antibodies circulate through the body fluids(humours),

the protection afforded by B cells is called humoral immunity.the protection afforded by B cells is called humoral immunity.

Structure of antibodies (Y-shaped proteins)

So what does an So what does an antibody do?antibody do?

1.1. Binds to molecules Binds to molecules (antigens) on the surface (antigens) on the surface of invading organism.of invading organism.

2.2. Inactivates or renders the Inactivates or renders the microorganism susceptible microorganism susceptible to destruction by the to destruction by the immune system.immune system.

ELISA TEST-One Way to Test for AntibodiesELISA 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 immunityCell-mediated immunity

It is an immune response that It is an immune response that does not involve does not involve antibodiesantibodies, , but ratherbut rather the cells act as the killers the cells act as the killers themselves.themselves.

It protects the body by:It protects the body by:

Activating antigen-specific Activating antigen-specific T-cellsT-cells that destroy that destroy infected cells.infected cells.

Activating Activating macrophagesmacrophages that destroy that destroy intracellular pathogens.intracellular pathogens.

Activating Activating NK (Natural Killer)NK (Natural Killer) cells that release cells that release a protein that kills the target cellsa protein that kills the target cells

Review 1Review 1

What is the enemy called that invades the What is the enemy called that invades the cell?cell?

What keeps intruders out?What keeps intruders out?

What are the two kinds of immunity?What are the two kinds of immunity?

Surface Barriers or Mucosal Surface Barriers or Mucosal ImmunityImmunity

SkinSkin

CiliaCilia

Tears, Saliva, Urine.Tears, Saliva, Urine.

Sticky mucusSticky mucus

Stomach: Stomach: Hydrochloric AcidHydrochloric Acid

AnalogyAnalogy

Suppose the classroom is a body.Suppose the classroom is a body. All students are cells.All students are cells. Rats are Rats are AntigensAntigens.. Doors and Windows prevent them from entering Doors and Windows prevent them from entering

- - Surface BarriersSurface Barriers.. Some of you Some of you Tough onesTough ones (T-cells) (T-cells) will capture will capture

the rodents - the rodents - Cell-mediated ImmunityCell-mediated Immunity.. Some of you Some of you BrainiacsBrainiacs (B-cells) (B-cells) will call pest will call pest

control (control (AntibodiesAntibodies) to capture the rodents – ) to capture the rodents – Humoral ImmunityHumoral Immunity..

What do these components look What do these components look like?like?

Source: National Library of Medicine

White Blood Cells:

Other Blood Components:

The Role of NeutrophilsThe 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 The Role of

Turn into MacrophagesTurn into Macrophages

Note the notch in the nucleus. Otherwise, it looks like a

lymphocyte.

MonocytesMonocytes EosinophilsEosinophilsAttack Internal ParasitesAttack Internal Parasites

Note the red granules in the cytoplasm.

Role of Role of LymphocytesLymphocytes

They play a major role in defending the host from both They play a major role in defending the host from both tumors and virally infected cellstumors and virally infected cells

There are two main types of lymphocytes: B cells and T There are two main types of lymphocytes: B cells and T cells. cells.

The B cells make antibodies that attack bacteria and toxins The B cells make antibodies that attack bacteria and toxins while the T cells attack body cells themselves when they while the T cells attack body cells themselves when they have been taken over by viruses or have become have been taken over by viruses or have become cancerous. cancerous.

They are often present at sites of chronic inflammation.They are often present at sites of chronic inflammation.

The Role of MacrophagesThe Role of MacrophagesEngulf and then digest cellular debris and Engulf and then digest cellular debris and

microbes in the body tissues.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 PlateletsThe Role of Platelets

Blood ClottingBlood 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 ReviewStop and Review

What are the types of white blood cells?What are the types of white blood cells?

What is the function of each of the types of What is the function of each of the types of white blood cells?white blood cells?

What is the role of platelets?What is the role of platelets?

Complete Blood Count (CBC)Complete Blood Count (CBC) Whether it is a human, dog, cat, steer, bird Whether it is a human, dog, cat, steer, bird

or even ferret, when sick, their doctors or even ferret, when sick, their doctors typically draw a blood sample and perform typically draw a blood sample and perform some tests to help determine a diagnosis. some tests to help determine a diagnosis.

The first test generally used is the The first test generally used is the complete blood count (CBC), which complete blood count (CBC), which determines the number and types of blood determines the number and types of blood cells present.cells present.

This test can provide information about the This test can provide information about the status of the patient’s immune system. status of the patient’s immune system.

Complete Blood Count (CBC)Complete Blood Count (CBC)

Blood is tested for Blood is tested for several things:several things:Red Blood CellsRed Blood Cells

White Blood CellsWhite Blood Cells

• Total count and percent Total count and percent values for each type of values for each type of white blood cellwhite blood cell

PlateletsPlatelets

Other blood componentsOther blood components• hemoglobinhemoglobin

• hematocrithematocrit

Click Here for a chart of normal blood values in dogs and cats

LeukocytosisLeukocytosis

Leukocytosis: Leukocytosis: white blood cell count white blood cell count increasedincreased above the normal range. above the normal range.

It is not a disorder or a disease, but a It is not a disorder or a disease, but a signsign of illness. of illness.

It occurs in response to a wide variety of It occurs in response to a wide variety of conditions, including conditions, including viral, bacterial, fungal, or parasitic viral, bacterial, fungal, or parasitic

infectioninfectioncancer cancer Hemorrhage (internal bleeding)Hemorrhage (internal bleeding)exposure to certain medications or exposure to certain medications or

chemicals including steroids.chemicals including steroids.

LeukopeniaLeukopenia

LeukopeniaLeukopenia: a : a decreasedecrease in the in the number of circulating white blood cells number of circulating white blood cells in the blood.in the blood.

As white blood cells get “used up” As white blood cells get “used up” during infection, leukopenia can place during infection, leukopenia can place patients at higher risk for infection.patients at higher risk for infection.

Causes: Causes: Influenza, typhus, malaria, Influenza, typhus, malaria, HIVHIV, tuberculosis, , tuberculosis,

dengue, Rickettsial infections, enlargement of the dengue, Rickettsial infections, enlargement of the spleen and folate deficiencies.spleen and folate deficiencies.

chemotherapy, radiation therapy, leukemia , chemotherapy, radiation therapy, leukemia , myelofibrosis and anemia.myelofibrosis and anemia.

many common medications like minocyclen. many common medications like minocyclen.

Immune Disorders in Humans and Immune Disorders in Humans and Animals:Animals:

HIV (Human Immunodeficiency Virus)HIV (Human Immunodeficiency Virus)

HIV infection in humans causes AIDS (HIV infection in humans causes AIDS (Acquired Acquired Immunodeficiency SyndromeImmunodeficiency Syndrome). ).

AIDS causes the immune system to fail, leading to life-AIDS causes the immune system to fail, leading to life-threatening opportunistic infections. threatening opportunistic infections.

Infection with HIV occurs by the transfer of blood, Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, pre-ejaculate, or breast milk.semen, vaginal fluid, pre-ejaculate, or breast milk.

The four major routes of transmission areThe four major routes of transmission are unprotected sexual intercourse,unprotected sexual intercourse, contaminated needles contaminated needles breast milkbreast milk transmission from an infected mother to her baby at birth.transmission from an infected mother to her baby at birth.

AIDSAIDS ( (Acquired ImmunoDeficiency SyndromeAcquired ImmunoDeficiency Syndrome))

Virus infects vital cells such as helper T cells and Virus infects vital cells such as helper T cells and macrophages.macrophages.

When When T cell numbers declineT cell numbers decline below a critical level, below a critical level, cell- cell-mediated immunity is lostmediated immunity is lost, and , and infectionsinfections with a variety of with a variety of opportunistic microbes appear.opportunistic microbes appear.

Illustration of the AIDS virus

penetrating a white blood cell and duplicating.

Similar to HIV, FIV is a condition in cats that is caused by a 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 virus and causes a reduction in the ability of the immune system of the cat to fight infection and illness.system of the cat to fight infection and illness.

It is sometimes known as Feline AIDS.It is sometimes known as Feline AIDS.

You can't catch AIDs from a catYou can't catch AIDs from a cat and a cat can't catch AIDs and a cat can't catch AIDs from an HIV infected person. This is not a zoonotic disease.from an HIV infected person. This is not a zoonotic disease.

Feline Immunodeficiency VirusFeline Immunodeficiency Virus(FIV)(FIV)

Click here for more information about FIVSee slide note for more resources

FIV continuedFIV continued Transmission: Bite wounds from infected cats, especially Transmission: Bite wounds from infected cats, especially

during cat fights, rarely by milk or during birth.during cat fights, rarely by milk or during birth.

Infected cats may appear normal for years. However, Infected cats may appear normal for years. However, infection eventually leads to a state of immune deficiency. infection eventually leads to a state of immune deficiency. The same agents found in the everyday environment--where The same agents found in the everyday environment--where they usually do not affect healthy cats--can cause severe they usually do not affect healthy cats--can cause severe illness in cats with weakened immune systems. illness in cats with weakened immune systems.

There is now also a There is now also a vaccine to help protect vaccine to help protect cats from FIV, however cats from FIV, however it does not provide it does not provide complete protection.complete protection.

Cat with Feline Immunodeficiency Virus

Caused by a virus similar to HIV and FIV.Caused by a virus similar to HIV and FIV.

Transmitted in the saliva and nasal secretions of infected Transmitted in the saliva and nasal secretions of infected cats.cats.

Also transmitted by urine, feces and milk.Also transmitted by urine, feces and milk.

Unsupervised outdoor cats are most at risk.Unsupervised outdoor cats are most at risk.

This infection can lead to cancer in cats, blood disorders, This infection can lead to cancer in cats, blood disorders, and immunodeficiency which causes cat to be unable to and immunodeficiency which causes cat to be unable to protect itself against infections.protect itself against infections.

There is a vaccine available for FeLV.There is a vaccine available for FeLV.

Feline Leukemia Virus (FeLV) Feline Leukemia Virus (FeLV)

Click here for more information on FeLV

A recessive genetic disorder that affects Arabian horses. This condition is A recessive genetic disorder that affects Arabian horses. This condition is fatal, as the animal inevitably succumbs to an opportunistic infection within fatal, as the animal inevitably succumbs to an opportunistic infection within the first four to six months of life.the first four to six months of life.

Carriers, who themselves are not affected by the disease, can be detected 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 with a DNA test. Careful breeding practices can avoid the risk of an affected foal being produced.foal being produced.

Dogs are also known to have SCID. There are two known forms, an X-linked 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 SCID in Basset Hounds, and a recessive form seen in one line of Jack Russell Terriers that is similar to SCID in Arabian horses.Russell Terriers that is similar to SCID in Arabian horses.

Severe Combined Immunodeficiency Severe Combined Immunodeficiency Disease in Animals (SCID)Disease in Animals (SCID)

Review 3Review 3

What is a CBC?What is a CBC?

What is Leukopenia and what are its causes?What is Leukopenia and what are its causes?

What is Leukocytosis and what could it be an What is Leukocytosis and what could it be an indicator of?indicator of?

Name four immune disorders and tell what Name four immune disorders and tell what causes them and what species they affectcauses them and what species they affect