Innate Immunity

Describe the response time between innate and adaptive immunity

Innate: Rapid response within hours

Adaptive: Slow response (takes 3-5 days to get started)

Describe the number of antigens the innate and adaptive immunity can see

Innate: Fixed number of antigens

Adaptive: Infinite amount of antigens

Is innate immunity specific? Adaptive?

Limited number of specificities in innate but numerous highly selective specificities in adaptive.

What is the difference between the course of response for innate and adaptive?

Innate is constant during the whole response (technically goes up and down) (default on) while adaptive immunity will improve over the period of infection

What are two common features among innate and adaptive immunity?

1. Common effector mechanisms for the destruction of pathogens

2. Have receptors that are recombined from the genomic DNA

What is the goal of the adaptive immune system? When is it the strongest?

To kill the pathogen. strongest after a week or two

What are the four lines of defense?

1. Physical and chemical barriers

2. Local non-immune cells

3. Sentinel cells and molecules

4. Circulating/ready-made effector cells and molecules

What are two examples of local non-immune cells?

1. Epithelial cells

2. M cells

What is the skin made up of?

1. Epidermis (uppermost layer)

2. Dermis (below epidermis)

What type of barrier does the skin act as?

A mechanical barrier impermeable to most infectious agents

What is the epidermis?

It is several layers of epithelial cells with the outermost layer that contains dead cells filled with keratin

What is keratin?

It is a waterproofing protein

Why is it challenging for pathogens to get into the skin?

This is because there are tight junctions between the epithelial cells that make up the skin which make it challenging to get in.

How do microbes get deleted on the skin?

Epithelial cells grow from the bottom up so when dead cells have reached the top they get recycled.

What type of barrier are mucus membranes? What are they made up of?

Chemical and mechanical. Made up of epithelium.

Where are mucus membranes found? What do they secrete? How do they trap pathogens?

They line the interior surfaces of the body (lung, gut) and secrete mucus. The mucus will trap foreign particles such as bacteria that prevents them from adhering to epithelial cells. Epithelial cells is how bacteria get into the body.

How are pathogens caught in mucus from the mucus membranes expelled?

Through mechanical action performed by the cilia and by sneezing, coughing and swallowing

What do normal bacterial flora/commensal microflora do?

They inhibit the growth of many potentially pathogenic bacteria. They act as a competitive barrier for non-microflora pathogens. This is also where non-dangerous pathogens live all the time

What do gut commensals produce?

Protective peptides

What are two features the gastrointestinal tract has?

1. Enzymes

2. Normal flora

What are two features the respiratory tract has?

1. Mucus

2. Mechanical action of cilia

What are two features the urogenital tract has?

1. Mucus

2. Fluid flow

What is a common mechanical feature shared by the skin, gut, lungs, and eyes/nose/oral cavity?

Epithelial cells joined by tight junctions

What is a common mechanical feature shared by the skin and gut? How is this a barrier?

Longitudinal flow of air or fluid. The air is constantly moving across us so the microbes don’t get a chance to attach

What are two chemical features that the skin has?

1. Fatty acids

2. Antimicrobial peptides (found in the mucus)

What are cilia? What is their purpose with immunity?

They are a hair-like organelle that move back and forth rhythmically. They keep microbes from attaching

Is the skin, gut, lungs, and eyes/nose/oral cavity all lined with epithelial cells? What are these four?

Yes and they are the four entryways for pathogens (anatomic barriers to infection)

What are three chemical features of the gut?

1. Low pH

2. Antimicrobial enzymes

3. Antimicrobial peptides

What is a mechanical feature of the lungs?

Movement of mucus by cilia

What are two chemical features of the lungs?

1. Pulmonary surfactant

2. Antimicrobial peptides

What are two mechanical features of the eyes/nose/oral cavity?

1. Tears

2. Nasal cilia

What are two chemical features of the eyes/nose/oral cavity?

1. Antimicrobial enzymes in tears and saliva

2. Antimicrobial peptides

What is constantly going through the gut? What does this result in?

Fluid which results in excretion of microbes

What is pulmonary surfactant?

It is a gooey substance made up of carbs, lipids, and proteins

What are the 2 functions of pulmonary surfactant?

1. Prevent alveoli in the lungs from collapsing

2. Chemical barrier that will trap the microbes that are breathed in

What type of mechanism are tears? What do antimicrobial peptides do?

Flushing mechanism. They disrupt the bacteria

What is the common set up for cellular barriers?

1. Commensal microflora

2. Epithelial and associated cells

3. Sentinel cells

What are the three roles of the commensal microflora? Does it have a low pH?

1. Maintain balence

2. Help with digestion

3. Crowd out pathogens

Yes low pH

Are there immune cells in the epithelial layer and below it? What is the role of the epithelial and associated cells?

Yes

1. Produce mucus or antimicrobial peptides/chemicals

What are the three roles of the sentinel cells?

1. Tolerance to commensal microflora

2. First line of detection for infection

3. Differ based on location

What immune cells are found in the epidermis layer?

1. CD8+ T cells (tissue resident memory T cells)

2. Langerhans cells (skin dendritic cells)

What immune cells are found in the dermis layer?

1. ILC

2. CD4+

3. Mast cell

4. Macrophage

5. Dermal DC

What happens once the tissue resident memory T cells get formed?

They are able to go back to the site of initial invasion of that microbe and live there longterm until they recognize something

Are immune cells within the physical barrier?

Yes