Class 17 Innate Immunity Overview

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Questions and Answers

What is the primary role of basophils in the immune system?

Facilitation of allergic reactions and inflammation (correct)

Production of antibodies

Detection of viral infections

Phagocytosis of pathogens

Which of the following cells primarily are responsible for host defense and housekeeping in tissues?

Natural Killer Cells

Dendritic Cells

Monocytes (correct)

Basophils

What is one of the functions of cytokines in the immune system?

Directly kill infected cells

Facilitate communication between cells (correct)

Generate antibodies

Process viral RNA

What type of immunity are B-cells primarily associated with?

Humoral immunity Signup and view all the answers

What does the term 'innate' refer to in the context of immune responses?

Response that is present from birth Signup and view all the answers

Which cytokine is most associated with regulating immune responses and controlling viral infections?

Interferon Signup and view all the answers

What complication can arise from the overproduction of cytokines in response to certain pathogens?

Cytokine Storm Signup and view all the answers

What is the primary role of barriers in the innate immune system?

To prevent entry of infectious agents Signup and view all the answers

What is the primary function of Dendritic Cells in the immune system?

Acting as sentinel cells and presenting materials to other immune cells Signup and view all the answers

Which of the following is NOT an issue with the skin as a barrier?

High permeability to pathogens Signup and view all the answers

How does the mucosal membrane function as both a barrier and a door?

It sheds outer layers but remains moist for transport. Signup and view all the answers

Which immune cells are part of the innate immune response with the ability to kill infected or abnormal cells?

Natural Killer Cells Signup and view all the answers

What is the primary purpose of the secretion of mucous in mucosal membranes?

To facilitate movement of pathogens out of the body Signup and view all the answers

What type of agents do sensors in the innate immune response detect?

Common pathogens and their signatures Signup and view all the answers

Which of the following correctly describes the outermost layer of skin?

It is dead and keratinized to prevent pathogen entry. Signup and view all the answers

What type of substances do mucosal membranes secrete to help kill pathogens?

Antimicrobial enzymes and peptides Signup and view all the answers

What is the primary function of lysozyme?

Degrades peptidoglycan Signup and view all the answers

Which class of white blood cells is known for having a short lifespan, typically measured in hours?

Neutrophils Signup and view all the answers

How do normal flora help prevent infections?

By consuming available nutrients Signup and view all the answers

What role do defensins play in the immune response?

Form pores in microbial membranes Signup and view all the answers

Which type of cell is primarily involved in clotting?

Platelets Signup and view all the answers

What characteristic is unique to eosinophils?

Their granules stain dramatically with eosin Signup and view all the answers

Which of the following is NOT a function attributed to normal flora?

They act as white blood cells Signup and view all the answers

What type of white blood cell has a nucleus that fills most of the cell?

Lymphocytes Signup and view all the answers

What is the primary role of cytokines in the inflammatory response?

To mark the area of infection and attract help. Signup and view all the answers

Which of the following terms refers to inflammation?

Itis Signup and view all the answers

How do blood vessels respond during inflammation?

They become leaky and increase in size. Signup and view all the answers

Which of the following is a symptom commonly associated with the body's inflammatory response?

Pus formation Signup and view all the answers

What can excessive inflammation lead to in the case of a blood infection?

Systemic inflammation and shock. Signup and view all the answers

Chronic inflammation can be caused by all the following EXCEPT?

Acute viral infection Signup and view all the answers

What is a cytokine storm?

Excessive release of cytokines leading to systemic inflammation. Signup and view all the answers

What effect do proinflammatory cytokines have on the body’s thermostat?

They cause it to reset to a higher temperature. Signup and view all the answers

What is the primary function of the complement system?

Amplifying immune responses against invaders Signup and view all the answers

Which of the following correctly describes the activation of the complement system?

It involves cleaving C3 to initiate a cascade. Signup and view all the answers

What role do macrophages play in the immune system?

They phagocytize and help recruit other immune cells. Signup and view all the answers

Which statement best describes the relationship between phagocytosis and macrophages?

Macrophages perform phagocytosis as part of the immune defense. Signup and view all the answers

What is a possible outcome of the activation of C3b in the complement cascade?

Promote opsonization of pathogens. Signup and view all the answers

What is the primary function of inactive viral proteins (iAVPs) when a cell is primed?

Degrade all mRNA upon detection of a virus Signup and view all the answers

Which of the following triggers the complement system?

Strange sugars and bound antibodies. Signup and view all the answers

Which receptors are responsible for detecting various microbial patterns?

Pattern Recognition Receptors (PRRs) Signup and view all the answers

Which of the following is a common type of Pattern Recognition Receptor found in the membranes of sentinel cells?

Toll-like Receptors (TLRs) Signup and view all the answers

What is the significance of granulomas in the immune response?

They wall off organisms that may still be alive. Signup and view all the answers

How does the immune system control the complement cascade?

Through multiple control and inactivation steps. Signup and view all the answers

What initiates the activation of iAVPs in a cell?

Presence of a virus in the primed cell Signup and view all the answers

Which of the following is not a type of damage-associated molecular pattern (DAMP)?

Peptidoglycan Signup and view all the answers

Where are cytoplasmic pattern recognition receptors (PRRs) primarily classified?

By RIG-like and NOD-like receptors Signup and view all the answers

Which type of TLRs would be responsible for monitoring the extracellular environment?

Surface TLRs Signup and view all the answers

What is one outcome of when a virus is detected in a primed cell?

Induction of apoptosis in that cell Signup and view all the answers

Study Notes

Innate Immunity

Innate immunity is present from birth
It defends the body against common threats
Barriers prevent entry of infectious agents
Sensors detect signs of external agents
Effectors quickly respond to general threats

Barriers: Skin

Multiple layers of epithelial cells
Outermost layers are dead and keratinized
Hard for pathogens to penetrate
Hostile environment (arid, high salt)
External layer sheds, removing pathogens
Effective barrier in most cases
Issues with degradation from moisture
Mechanical abrasion or penetration
Penetration by specialized biochemistry (e.g., parasites)
Limited in nutrient/waste exchange

Barriers: Mucosal Membranes

Areas needing transport and moisture
Barriers and doors simultaneously
Contained spaces, making shedding difficult
Mucosal Membranes: Shed and Wash
Secrete sticky mucus
Move mucus to disposal areas
Shed cells along the way for additional defense

Mucosal Membrane – Antimicrobial Substances

Wide range of killing enzymes and peptides (e.g., lysozyme, peroxidases)
Break down hydrogen peroxide
Lactoferrin and transferrin bind iron (required for many microbes to grow)
Specialized defense peptides (HDPs)
Defensins form pores in microbial membranes

Recruiting Microbial Allies – Normal Flora

Competitive exclusion of pathogens
Consume available nutrients
Production of toxic compounds (e.g., fatty acids from Cutibacterium species)
Beneficial bacteria (e.g., E. Coli and lactobacilli) produce substances to protect from pathogens

Defenses in Blood and Lymph

Specialized cells derived from hematopoietic stem cells
Three general classes:
- Red blood cells (erythrocytes): oxygen transport
- Platelets (thrombocytes): clotting
- White blood cells (leukocytes): body defenses

White Blood Cells

Originally categorized by microscopic appearance
Granulocytes (e.g., neutrophils, eosinophils, basophils)
Granules in the cytoplasm seen via specific stains
Mononuclear phagocytes (e.g., monocytes, macrophages, dendritic cells)
Smooth nucleus with clear cytoplasm
Lymphocytes (covered in a separate section)

Granulocytes (Neutrophils, Eosinophils, Basophils)

Neutrophils: short lifespan, major component of pus, kill by fusing with granules, attack by degranulating, increase with infection
Eosinophils: combat parasites and allergies
Basophils: contain histamine, roles in allergic reactions and inflammation

Mononuclear Phagocytes (Monocytes, Macrophages, Dendritic Cells)

Monocytes: circulate in blood, become macrophages in tissues, professional phagocytes, specialized by tissue, host defense, housekeeping
Macrophages: engulf and destroy pathogens
Dendritic cells: sentinel cells that collect material from wide area, present to other immune cells

Lymphocytes

Major part of adaptive immunity
Two primary subtypes (B-cells and T-cells) with similar appearance
B-cells: humoral immunity (antibodies)
T-cells: cellular immunity (attack infected cells)
Natural Killer cells: innate ability to kill certain types of cells

Cell Communication

Cytokines, chemokines, colony-stimulating factors (CSFs), interferons (IFNs), interleukins (ILs), tumor necrosis factor (TNF)
Cytokine storms: overproduction of cytokines in response to certain pathogens

What Triggers a Response?

Pattern Recognition Receptors (PRRs) recognize indicators of attack (Microbes, Pathogens, Damage):
- Pathogen-associated molecular patterns (PAMPs)
- Damage-associated molecular patterns (DAMPs)
- Microbe-associated molecular patterns (MAMPs)

PRRs in Cytoplasm

Book classifies PRRs by "RIG-like" (RLRs) and "NOD-like" (NLRs)
Function to detect and identify markers of microbial and cellular damage

Soluble Enzymes in a Cascade

Required proteins are often present in inactive precursors
Multiple activation steps amplifying the response rapidly

Complement

Consisting of multiple proteins working together (C1-C9)
Initiated by multiple triggers including invading microorganisms, lectins, and antibodies
Potential effects include opsonization, inflammation, and membrane punching

Phagocytosis

Phagocytes "eat" by grabbing suspicious material
Surround the material with pseudopods
Direct lysosomes to fuse, digesting contents
Phagocytosis is essential for debris removal

Macrophages

Professional phagocytes
Pick up everything: dead cells, trash, invaders
Live for weeks/months
Alert and recruit other immune cells
Granulomas to wall off disease-causing agents

Inflammatory Response

PRRs (or complement) detect invaders
Cytokines mark the area, attract help (neutrophils)
Cause blood vessels to increase in size and become leaky to allow movement of leukocytes into tissue
Stimulates adhesion molecules on epithelial cells
Usually controlled but some areas are more sensitive to inflammation

Inflammation (-itis)

"-itis" suffix means inflammation
Examples: gastritis, meningitis, otitis media, gingivitis
Common symptoms like swelling and redness are caused by inflammatory mediators

Excessive Inflammation

Blood infections (sepsis) can lead to systemic inflammation ("shock")
Toxins induced stimulation
Cytokine storm
Chronic inflammation is part of several conditions (e.g., Rheumatoid Arthritis) or chronic stress, obesity, excessive red meat

Fever

Proinflammatory cytokines reset the body's thermostat to a higher temperature
Inhibit microbial growth, increase metabolism of immune cells, and increase efficiency of antimicrobial enzymes

Homework: Macrophages and Tattoos

Investigate the link between macrophages and tattoos,
Assess the net effect on the structure and duration of the tattoo, and
Provide a citation.

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Description

Explore the basics of innate immunity, which provides the body's first line of defense from birth. Learn about the crucial barriers like skin and mucosal membranes that prevent infection, as well as the mechanisms involved in detecting and responding to threats. This quiz will help reinforce your understanding of how these innate defenses function.