chapter 16 microbiology

What is immunity?

The body’s ability to resist disease and infection.

What is susceptibility?

The likelihood of developing disease when exposed to a pathogen (lack of protection).

What is innate immunity?

Nonspecific immunity that is present at birth, acts immediately, and does not have memory.

What is adaptive immunity?

Specific immunity that develops after exposure, takes time to respond, and has memory.

What is the main function of the first line of defense?

To prevent microbes from entering the body.

Why is unbroken skin important in innate immunity?

It acts as a physical barrier that blocks microbes from entering.

What are mucous membranes?

Thin, moist epithelial linings that secrete mucus to trap microbes.

Where are mucous membranes found?

Respiratory tract, gastrointestinal tract, genitourinary tract, and eyes.

What is the role of mucus in innate immunity?

It traps microbes and prevents them from reaching underlying tissues.

How do eyes and the lacrimal apparatus contribute to innate immunity?

Tears wash away microbes and contain lysozyme, which destroys bacteria.

How does saliva help protect the body?

It washes away microbes and contains lysozyme.

How does urine function as a defense?

It flushes microbes out of the urinary tract.

Why is the vaginal tract considered part of the first line of defense?

It is acidic, which inhibits pathogen growth.

How do fatty acids in sebum and earwax protect the body?

They lower pH and inhibit microbial growth.

What antimicrobial role does perspiration (sweat) play?

It contains substances that inhibit microbial growth.

What is lysozyme and where is it found?

An enzyme that breaks down bacterial cell walls; found in saliva, tears, sweat, and nasal secretions.

Why are acidic areas important in innate immunity?

They kill or inhibit microbes. Examples: stomach, vagina, urine/urethra.

What is the role of normal microbiota in innate immunity?

They compete with pathogens for nutrients and space and produce antimicrobial substances.

When does the second line of defense act?

After microbes have entered the body.

What role does blood play in innate immunity?

It transports leukocytes, complement proteins, and antimicrobial substances.

What is the function of the lymphatic system?

To return tissue fluid to blood, transport immune cells, and filter pathogens via lymph nodes.

What are the two most common phagocytes?

Neutrophils and macrophages.

What is chemotaxis?

Movement of phagocytes toward chemical signals released by microbes or damaged tissue.

What is adherence in phagocytosis?

The attachment of a phagocyte to a microbe.

What is opsonization?

Coating of microbes with antibodies or complement to make them easier to engulf.

What happens during ingestion in phagocytosis?

The phagocyte extends pseudopods and encloses the microbe in a phagosome.

What do lysosomes do?

They contain enzymes that digest and destroy microbes.

What is a phagolysosome?

A phagosome fused with a lysosome for microbial digestion.

If a microbe prevents adherence of phagocytes, what happens?

It has a greater chance of spreading through the body.

What are the three stages of inflammation?

1. Vasodilation & increased permeability 2. Phagocyte migration 3. Tissue repair

Why do vasodilation and increased permeability occur?

To increase blood flow and allow immune cells and proteins to enter infected tissue.

What is the role of histamine?

Increases blood vessel permeability.

What do kinins do in inflammation?

Cause pain and swelling.

What do prostaglandins do?

Promote inflammation and pain.

What are cytokines?

Chemical messengers that regulate immune responses.

What is margination?

Phagocytes lining up along blood vessel walls.

What is diapedesis?

Phagocytes squeezing through blood vessel walls into tissues.

Which cells arrive first at an infection site?

Neutrophils, followed by monocytes (which become macrophages).

What part of the brain controls body temperature?

The hypothalamus.

What bacterial component can trigger fever?

Lipid A from Gram-negative bacteria.

Why do blood vessels constrict during fever?

To conserve heat and raise body temperature.

How does fever act as a defense?

It slows microbial growth and enhances immune responses.

What is the complement system?

A group of over 30 proteins in blood that destroy pathogens via a cascade.

What activates the classical complement pathway?

Antibody–antigen complexes.

What are three effects of complement activation?

• Cytolysis (MAC formation) - Opsonization - Inflammation

What are interferons?

Cytokines that protect against viral infections.

What do IFN-α and IFN-β do?

Make nearby cells resistant to viral infection.

What does IFN-γ do?

Activates macrophages and NK cells.

How do iron-binding proteins help immunity?

They limit free iron so bacteria cannot grow efficiently.

Name four iron-binding proteins.

Transferrin, lactoferrin, ferritin, hemoglobin.

What are antimicrobial peptides (AMPs)?

Small proteins that kill microbes by disrupting their membranes.

How do antimicrobial peptides increase innate immunity?

By directly killing bacteria, fungi, and some viruses.