Chapter 3 - Innate Immune Responses (Part 2)

What is the role of innate immunity?

Acts immediately to remove pathogens without disease development.

When is adaptive immunity required?

If innate immunity is overwhelmed, bypassed, or evaded by pathogens.

What causes inflammation?

Physical/chemical insult or infection with microorganisms.

What are the two types of inflammation?

• Acute inflammation (short-term, minor tissue damage)

• Chronic inflammation (long-term, significant tissue damage).

What is chronic inflammation characterized by?

Activated macrophages, T cells, and persistent tissue destruction.

What initiates the inflammatory response in bacterial infections?

Activation of the alternative complement pathway and tissue-resident macrophages detecting bacterial PAMPs.

What do tissue-resident macrophages use to recognize bacteria?

Pattern recognition receptors (PRRs) bind to bacterial structures.

What does a Toll-like receptor (TLR) bind to?

Pathogen-associated molecular patterns (PAMPs).

What happens after PAMP-TLR binding?

NF-κB transcription factor is activated, leading to pro-inflammatory cytokine production.

What cells initiate the inflammatory response at the infection site?

Macrophages and mast cells.

What is the role of histamine?

Dilates blood vessels, increasing blood flow, causing redness & heat.

What increases vascular permeability?

Cytokines (IF-1, IF-6) from resident macrophages, allowing fluid, proteins, and immune cells to enter tissues.

What is extravasation?

The movement of leukocytes (neutrophils, monocytes) through blood vessel walls into tissues.

Which cells are recruited in large numbers within hours?

Neutrophils and monocytes.

What is a phagosome?

A membrane-bound vesicle that engulfs bacteria inside a phagocyte.

How are pathogens killed inside the phagolysosome?

Nitric oxide (NO), superoxide anion (O2–), hydrogen peroxide (H2O2), defensins, and proteases.

Why is clotting activated?

To wall off the infection and prevent bacterial spread.

What is pus composed of?

Macrophages, neutrophils, dead cells, bacteria, and plasma.

How does the complement system help?

Enhances recruitment, phagocytosis, and pathogen destruction.

What does histamine do in inflammation?

Increases blood vessel permeability, allowing immune cells to reach the infection site.

What do macrophages and neutrophils do?

Phagocytose and destroy pathogens.