041 immunity final

What is innate immunity?

Defenses present at birth.

How quickly does innate immunity respond to infection or injury?

It responds rapidly.

What does innate immunity recognize?

Broad microbial patterns, not specific strains.

What does innate immunity include?

Barriers, inflammation, phagocytes, complement, interferons.

What does innate immunity do for adaptive immunity?

Buys time for adaptive immunity to develop.

What is the 1st line of defense?

Barriers that prevent entry.

What is the 2nd line of defense?

Innate responses that act after entry.

What is the 3rd line of defense?

Adaptive immunity, which targets specific antigens.

How do the lines of defense relate to each other?

They overlap and reinforce each other.

What role does innate immunity play regarding adaptive immunity?

Innate immunity helps activate adaptive immunity.

How does innate immunity compare to adaptive immunity in speed and specificity?

Innate: fast, broad, no prior exposure required. Adaptive: slower at first, highly specific.

What do innate receptors detect?

Shared microbial patterns.

What do adaptive receptors detect?

Specific antigens.

Do innate and adaptive immunity work separately or together during real infections?

Both systems work together during real infections.

Where do first line defenses act?

At body surfaces.

What types of barriers are included in the first line of defense?

Physical, mechanical, chemical, and microbial barriers.

What do normal microbiota do on body surfaces?

Occupy body surfaces, compete with pathogens for space and nutrients, produce inhibitory chemicals, help train and regulate immune responses.

What can happen if the microbiome is disrupted?

Disruption can allow opportunistic infections.

What are examples of chemical barriers mentioned in the slide?

Stomach acid, lysozyme, sebum and fatty acids, antimicrobial peptides

What do normal secretions do to body surfaces?

Make surfaces chemically difficult to colonize.

Can microbes be harmless in one location but dangerous in another?

Yes, microbes may be harmless in one location, dangerous in another.

What example shows normal flora entering deeper tissue through a skin break?

C. acnes entering deeper tissues through skin breaks.

How can aspiration cause infection?

Aspiration can move oral microbes into the lungs.

How do surgery and medical devices affect natural defenses?

Surgery and devices bypass natural defenses.

What does infection risk depend on?

Both the microbe and the portal of entry.

What chemical barrier does Helicobacter pylori survive in the stomach?

Stomach acid, by producing urease.

What does urease do?

neutralize acid nearby

Where does H. pylori colonize?

The mucus layer near stomach cells.

What can chronic H. pylori infection lead to?

Gastritis, ulcers, and cancer risk.

What does H. pylori's survival strategy show?

How pathogens evolve around innate defenses.

A patient is prescribed Levaquin (levofloxacin), a broad-spectrum fluoroquinolone antibiotic, for a respiratory infection and develops severe diarrhea a week later. Which innate defense was disrupted?

Normal microbiota

What do innate cells look for, rather than specific strains?

Patterns.

What are PAMPs?

microbial red flags

What are PRRs?

host sensors for infection

What does recognition of PAMPs/PRRs trigger?

Cytokines, inflammation, and phagocytosis.

How fast does the innate recognition response begin?

Within minutes to hours.

Are PAMPs shared by many microbes?

Yes, PAMPs are shared by many microbes.

What are examples of PAMPs?

LPS, flagellin, peptidoglycan, and viral RNA.

Why are PAMPs usually essential for microbial survival?

They are usually essential for microbial survival.

Are PAMPs found on healthy human cells?

They are rare or absent on healthy human cells.

What do PAMPs help immune cells do?

Detect infection quickly.

What does PRR activation trigger?

Cytokine release.

What do cytokines act as?

Immune communication signals.

What happens to nearby blood vessels after PRR activation?

They become activated.

What cells are recruited to the site after PRR activation?

Phagocytes.

What can happen later after PRR activation and phagocyte recruitment?

Adaptive immunity may be activated later.

What is sepsis?

Life-threatening organ dysfunction from infection.

What often triggers sepsis?

Strong innate immune activation.

What can PAMP detection trigger in sepsis?

Widespread cytokine release.

What happens to blood vessels in sepsis?

They become leaky and poorly regulated.

What is the core problem in sepsis?

The problem becomes host damage, not just microbes.

A macrophage detects bacterial flagellin using a surface receptor and releases cytokines that recruit more immune cells. What is the best explanation?

A PRR detected a PAMP

What does innate immunity use in body fluids?

Proteins dissolved in fluids.

Where are soluble innate immune proteins found?

Blood, lymph, mucus, and tissues.

What do soluble innate immune proteins help do?

Detect, tag, slow, or destroy microbes.

What are major examples of soluble innate defenses?

Acute phase proteins, complement, cytokines.

What happens to many soluble defenses during inflammation?

Many increase during inflammation.

Where are acute phase proteins produced mainly?

The liver.

When do acute phase proteins increase?

During infection, injury, or inflammation.

What does CRP do?

Helps tag microbes for phagocytosis.

What does transferrin do?

Limits free iron for bacteria.

What does mannose-binding lectin do?

Can activate complement.

What is the complement system?

A group of plasma proteins that activate in a cascade (innate and non-specific).

What are the three major outcomes of complement activation?

Opsonization, inflammation, lysis

Does complement work only with innate immunity?

No, it works with both innate and adaptive immunity.

What do opsonins do?

Coat microbial surfaces.

What happens to phagocytes when microbes are coated with opsonins?

Phagocytes bind coated microbes more efficiently.

What is a key complement opsonin?

Complement protein C3b.

Can antibodies act as opsonins?

Yes, antibodies can also act as opsonins.

What is the result of opsonization?

Faster phagocytosis.

What do all complement activation pathways converge on?

C3.

What are the outcomes shared by all complement activation pathways?

Opsonization, inflammation, lysis.

What is the membrane attack complex most effective against?

Some Gram-negative bacteria.

How are host cells protected from the membrane attack complex?

Host cells are protected by complement regulators.

What do virus-infected cells release?

Interferons.

What do interferons do to nearby cells?

Warn nearby cells.

What do nearby cells produce in response to interferons?

Antiviral proteins.

What effect do interferons have on viral replication?

Viral replication becomes harder.

What is the overall benefit of interferons?

Helps slow spread before adaptive immunity responds.

What are cytokines?

Short-range or systemic immune signals.

What do cytokines coordinate?

Inflammation, fever, and cell recruitment.

What produces cytokines?

Immune cells and infected tissues.

When are cytokines helpful vs harmful?

Helpful when controlled; harmful when excessive or widespread.

What can severe COVID-19 trigger?

Excessive cytokine release (cytokine storm).

What do cytokines do during a cytokine storm?

Recruit immune cells and increase inflammation.

What does a cytokine storm damage in the lungs?

The alveoli.

What does fluid leakage impair in severe COVID-19?

Gas exchange.

What can severe COVID-19 cytokine storm progress to?

ARDS and multi-organ damage.

What may treatment for severe COVID-19 target?

Both the virus and the host inflammatory response.

A bacterium becomes coated with C3b, and a neutrophil binds and engulfs it more easily. Which complement outcome is shown?

Opsonization

What is inflammation?

A local response to injury or infection.

What is the goal of inflammation?

To bring immune cells and proteins to affected tissue.

What does inflammation help accomplish?

Helps contain microbes and start repair.

What causes redness in inflammation?

Increased blood flow.

What causes heat in inflammation?

Warm blood entering the area.

What causes swelling in inflammation?

Fluid leaking into tissue.

What causes pain in inflammation?

Pressure and chemical mediators stimulating nerves.

What additional sign may occur in severe inflammation?

Loss of function.

What do cytokines and complement create that guides WBC movement?

Chemical gradients.

What happens to WBCs at vessel walls during recruitment?

They slow down and stick to vessel walls.