5.3 - 5.6 Responding to Antigens and Acquiring Immunity

What is the role of the immune system?

To distinguish self from non-self and eliminate pathogens while limiting damage to the body.

What are white blood cells also called?

Leukocytes

What are the three lines of defence?

1. First Line – Physical/Chemical/Microbiota barriers; 2. Second Line – Innate (non-specific); 3. Third Line – Adaptive (specific)

What are the first line of defence barriers?

Skin

What is innate immunity?

Non-specific defences present from birth

What is adaptive immunity?

Specific defences acquired over time that provide long-lasting protection.

What are the three barrier types in the first line of defence?

Physical

What are examples of physical barriers in animals?

Intact skin

What are examples of chemical barriers in animals?

Stomach acid

What does lysozyme do?

Breaks down bacterial cell walls

What are microbiological barriers?

Non-pathogenic flora that compete with pathogens for space and resources

What are examples of plant mechanical barriers?

Waxy cuticle

What are plant physical deterrents to pathogens?

Spines

What are plant chemical defences?

Phytoanticipins

What is phagocytosis?

The process of engulfing and digesting pathogens or debris by immune cells

What are the four types of phagocytes?

Neutrophils

What do neutrophils do?

Engulf pathogens

What do macrophages do?

Engulf dead cells/pathogens

What are monocytes?

Immature white blood cells that differentiate into macrophages

What do dendritic cells do?

Present antigens to T cells; found at environmental interfaces (e.g.

Where do dendritic cells migrate after antigen capture?

Lymph nodes and spleen to activate T cells

What are eosinophils?

White blood cells that attack large parasites and release histamine and toxic granules

What do Natural Killer (NK) cells do?

Destroy virus-infected and cancerous cells by releasing cytotoxic chemicals

What chemical do NK cells release?

Perforin – punches holes in infected cell membranes

What else do NK cells release to alert the immune system?

Cytokines

What are mast cells?

Cells in tissues that release chemicals to trigger inflammation

What do mast cells release?

Histamines

What do histamines do?

Increase blood vessel permeability and dilation; trigger inflammation

What are complement proteins?

Group of ~30 proteins in the blood that help destroy pathogens

How are complement proteins activated?

By contact with antigen-antibody complexes

Functions of complement proteins?

Lyse bacterial membranes

What are cytokines?

Signalling molecules that coordinate immune responses

Roles of cytokines?

Promote fever

What are interferons?

Cytokines released by virus-infected cells that interfere with viral replication

How do interferons help fight viruses?

Activate enzymes that degrade viral RNA and block translation

What are chemokines?

A type of cytokine that attracts leukocytes to infection sites

What triggers the inflammatory response?

Tissue damage or pathogen invasion

What are the signs of inflammation?

Redness

What releases histamines during inflammation?

Mast cells and basophils

What is the first step in inflammation?

Pathogen breaches the first line of defence (e.g.

What do chemokines do during inflammation?

Signal immune cells to the site of infection

What proteins arrive with the blood during inflammation?

Clotting factors

What immune cells arrive at the site of infection?

Neutrophils

What do neutrophils do at infection site?

Secrete hydrogen peroxide and phagocytose pathogens

What do macrophages do at infection site?

Release cytokines and phagocytose debris and pathogens

What is pus?

Dead white blood cells and pathogen debris

What is fever?

A rise in body temperature to slow pathogen growth and enhance immune activity

What causes fever?

Cytokines and bacterial toxins (pyrogens) resetting the hypothalamus temperature

Benefits of fever?

Slows bacterial replication