The Immune System

The Nature of Disease

Infectious Diseases: Diseases, such as colds, that are caused by pathogens that have invaded the body.

Pathogens include:– Bacteria– viruses – fungi – protists

Koch’s Postulate

The Spread of Disease

a. Air

b. Food

c. Water

d. Person-to-person contact

e. Bites by animals

Nonspecific Defenses

• Innate Immunity: Defenses that help protect the body against any pathogen, regardless of its identity.

First-line of Defense

Barriers:A. Skin- physical barrier to

pathogens.

B. Mucus Membrane- epithelial tissue that protect the interior surfaces of

the body.

Skin

• The skin blocks pathogens from entering the body.

• It also releases sweat, oils and waxes that contain chemicals that are toxic to pathogens.– ex. sweat contains lysozyme an enzyme

Mucus Membrane

• The mucus membrane serves as a barrier and secretes mucus. This is a sticky fluid that traps pathogens.

• Lines the respiratory and digestive systems and the urethra.

Second-line of Defense

When a pathogen gets past the first line of defense

A. Inflammatory Response- a protective response of tissue affected by disease or injury, characterized by redness, swelling and pain.– Histamine- is released by damaged cells and

increases blood flow to the area– Histamines attract white blood cells to the affected

area

Second line of Defense

Cells involved in the inflammatory response:• Phagocytes- Ingest and destroy pathogens

– Neutrophil- Ingest pathogens they encounter – Macrophage- engulfs pathogens and cellular debris.

White blood cells that attack pathogen-infected cells. ex. cancer and viruses

Second line of DefenseB. Temperature Response – a moderate fever may

slow bacterial and viral growth and promote white blood cell activity.

C. Proteins – Complement proteins circulate in the blood and become active when they encounter certain pathogens.– puncture membrane of infected cells– Interferon- released by virus-infected cells to help nearby cells resist infection

Specific Defense

The Immune System:

The cells and tissue that recognize and attack foreign substances in the body.

Components of Immune System

A. Lymphocytes – The white blood cells- B cells and T cells

B. Thymus - gland above the heart that helps produce a special kind of lymphocyte (T-cells)

C. Spleen – Stores healthy blood cells and helps develop lymphocytes and other white blood cells

Recognizing Pathogens

• Lymphocytes can recognize foreign invaders by their antigens.

• Antigens are any substance that the immune system can recognize and react with.

• Lymphocytes have unique receptor proteins bind to antigens and start a specific attack called an immune response.

Immune Response

1. Pathogen enters your bodya. Contains an antigen

2. Macrophages engulf (eat) these pathogens

3. Macrophages present the antigen on its surface

4. Helper T- cell recognizes this antigen with a receptor and is activated

Immune Response

5. Helper T cell activates B cell and it divides

6. B cells become plasma cells

7. Plasma cells secrete antibodies

8. Antibodies bind to antigen and mark them for destruction

Antibodies

• Antibodies – a protein that reacts to a specific antigen or that inactivates or destroys toxins

Innate vs. Acquired Immunity

• Innate Immunity: Skin barriers and body secretions– Not specific

• Acquired Immunity:

Specific response to a

specific antigen

Immunity and Vaccination

• Immunity – the ability to resist an infection disease

• Vaccination – the

introduction of antigens

into the body to cause

immunity.

Vaccine

• Vaccine - a solution that contains dead or weakened pathogens. Since the antigens are still present the body produces an immune response. Can be oral (live and weakened) or injected (heat-killed toxoid).

ex. Polio, measles, mumps, tetanus, small pox

Problems of the Immune System

When the immune system reacts to harmless antigens in ways that can be harmful.

• Allergies – physical response to an antigen.ex. pollen, animal dander and food.

• Asthma – a respiratory disorder that causes the bronchioles to narrow because of an overreaction to a substance in the air.

Problems

• Autoimmune Disease – when the immune system attacks the organism’s own cells

ex. Multiple sclerosis

Rheumatoid arthritis

Thyroiditis

Improper Functions

• AIDS (acquired immunodeficiency syndrome) – Causes the immune system to lose its ability

to fight off pathogens and cancers. Caused by the virus HIV that attacks the T cells.

– T-cells are not able to

activate proper immune

responses

Bacteria vs. Viruses

Bacteria Viruses

Bacteria Viruses

- Living - Non-living- Prokaryotes - parasite- treat with antibiotics - can not reproduce

on its own

- can not obtain itsown energy

Bacteria vs. Viruses

Bacteria vs. Viruses

Bacteria Viruses

• Replication: Non-living, require a

Binary Fission host to replicate

• Immune Response:

Antibodies, macrophages Antibodies, macrophages

• Treatment: Some antivirals, but normally

Antiobiotics No treatment

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