Lecture 18 Pt1- Innate Host Defense

Flashcard 1 Q: What does the immune system refer to?

A: The immune system refers to the ability of an organism to protect itself from pathogen infection.

Flashcard 2 Q: What is required for effective protection from infection?

A: The immune system must be able to determine the difference between self and non-self.

Flashcard 3 Q: Does the immune system always function properly?

A: No, the immune system does not always function properly.

Flashcard 4 Q: How does the body respond when exposed to a potential pathogen?

A: The body responds by activating defense mechanisms that protect itself from infection.

Flashcard 5 Q: What are the two major types of immunity?

A: Innate immunity and adaptive immunity.

Flashcard 6 Q: What is innate immunity?

A: Innate immunity consists of nonspecific mechanisms that try to prevent pathogens from entering the body and serve as the first line of defense.

Flashcard 7 Q: What are the major components of innate immunity?

A: Physical barriers, chemical barriers, cellular defenses, inflammation, fever, and molecular defenses.

Flashcard 8 Q: What is adaptive immunity?

A: Adaptive immunity is an antigen-specific response induced by the host immune system.

Flashcard 9 Q: How is adaptive immunity different from innate immunity?

A: Adaptive immunity is tailored to a specific pathogen and can generate antibodies to target potential pathogens

Flashcard 10 Q: What are physical barriers in nonspecific host defense?

A: Structures that physically block pathogens from entering the body.

Flashcard 11 Q: Which structures primarily act as physical barriers?

A: The skin and mucous membranes.

Flashcard 12 Q: What type of cells form physical barriers?

A: Epithelial cells.

Flashcard 13 Q: Why is skin considered the first line of defense?

A: It is constantly exposed to microorganisms and environmental stressors and provides a physical barrier.

Flashcard 14 Q: What cells make up the outer layer of skin?

A: Keratinocytes.

Flashcard 15 Q: What is keratin and what is its role?

A: Keratin is produced by keratinocytes and is used in the production of hair, nails, and skin.

Flashcard 16 Q: Are microorganisms present on the skin?

A: Yes, different niches of microorganisms reside on the skin.

Flashcard 17 Q: Why do different microorganisms live on different areas of the skin?

A: Because different microenvironments exist on the skin.

Flashcard 18 Q: What is the function of mucous membranes?

A: They cover tissues and organs and act as physical barriers.

Flashcard 19 Q: Which systems are protected by mucous membranes?

A: Respiratory tract, gastrointestinal (GI) tract, and genitourinary tract.

Flashcard 20 Q: How many microorganisms does an average person breathe in per day?

A: About 10,000 microorganisms per day.

Flashcard 21 Q: What happens to large microorganisms (>10 µm) in the respiratory system?

A: They are trapped by hairs and cilia in the nasal cavity.

Flashcard 22 Q: How do cilia help remove pathogens from the respiratory tract?

A: They beat toward the pharynx or mouth, allowing coughing or sneezing to expel microorganisms.

Flashcard 23 Q: What happens to small microorganisms (<10 µm) in the lower respiratory tract?

A: They are trapped in the mucociliary blanket.

Flashcard 24 Q: What clears microorganisms that reach the alveoli?

A: Alveolar macrophages.

Flashcard 25 Q: How are most ingested microorganisms killed in the GI tract?

A: By the acidic environment of the stomach (HCl and proteolytic enzymes).

Flashcard 26 Q: Which microorganisms can survive stomach acid?

A: Cysts, Helicobacter pylori, and Clostridium species.

Flashcard 27 Q: How does the GI tract physically remove pathogens?

A: Through peristalsis, shedding of epithelial cells, vomiting, and diarrhea.

Flashcard 28 Q: How are microorganisms typically cleared from the genitourinary tract?

A: By flushing with urine.

Flashcard 29 Q: Why is urine antimicrobial?

A: It has a low pH and contains urea and toxic end-products.

Flashcard 30 Q: Why are women more likely to develop UTIs?

A: Because women have a shorter urethra.

Flashcard 31 Q: What bacteria dominate the female vaginal microbiome?

A: Lactic-acid–forming Lactobacillus species.

Flashcard 32 Q: How does Lactobacillus protect against infection?

A: It creates an acidic environment that makes invasion difficult.

Flashcard 33 Q: What is lysozyme?

A: An enzyme found in tears, saliva, and mucus.

Flashcard 34 Q: How does lysozyme damage bacteria?

A: It cleaves the covalent bond between NAM and NAG in bacterial peptidoglycan.

Flashcard 35 Q: What is transferrin?

A: A soluble blood protein that binds iron.

Flashcard 36 Q: Why is iron binding important for host defense?

A: Bacteria require iron as a co-factor for growth.

Flashcard 37 Q: What is lactoferrin?

A: A protein in saliva and mucus that binds iron to prevent bacterial growth

Flashcard 38 Q: What are antimicrobial peptides?

A: Chemical mediators that act as part of innate immunity.

Flashcard 39 Q: What does amphipathic mean in antimicrobial peptides?

A: They have both hydrophobic and hydrophilic regions.

Flashcard 40 Q: How do antimicrobial peptides kill microorganisms?

A: By forming pores in membranes, causing lysis.

Flashcard 41 Q: What is the complement system?

A: A collection of serum proteins involved in innate immunity.

Flashcard 42 Q: What are the outcomes of complement activation?

A: Inflammation, microbial cell lysis, and opsonization.

Flashcard 43 Q: What is opsonization?

A: Coating microbes with opsonins to enhance recognition by phagocytes.

Flashcard 44 Q: In what form are complement proteins initially produced?

A: In an inactive form.

Flashcard 45 Q: How are complement proteins activated?

A: By a cascade of proteolytic cleavage.

Flashcard 46 Q: What are the three pathways of complement activation?

A: Alternative, lectin, and classical pathways.

Flashcard 47 Q: What type of bacteria activate the alternative pathway?

A: Bacteria with repetitive structures such as LPS in Gram-negative bacteria.

Flashcard 48 Q: What happens to C3 during alternative pathway activation?

A: It self-cleaves into C3a and C3b.

Flashcard 49 Q: What is the function of C3b?

A: It binds to bacterial surfaces and acts as an opsonin.

Flashcard 50 Q: Which complement fragment promotes inflammation?

A: C3a.

Flashcard 51 Q: How does C3a promote inflammation?

A: By stimulating vasodilation of host cells.

Flashcard 52 Q: What are cytokines?

A: Small soluble glycoproteins released by one cell that affect other cells.

Flashcard 53 Q: What stimulates cytokine production?

A: Bacteria, viruses, parasites, tumors, and inflammation.

Flashcard 54 Q: Can one cytokine influence others?

A: Yes, production of one cytokine can promote production of others.

Flashcard 55 Q: How do cytokines interact with target cells?

A: By binding to transmembrane receptors.

Flashcard 56 Q: Do cytokines need to bind in large amounts to cause effects?

A: No, small numbers can induce dramatic responses.

Flashcard 57 Q: What are chemokines?

A: Cytokines that stimulate migration of responsive cells to a site.

Flashcard 58 Q: What are interleukins?

A: Cytokines produced by one leukocyte to stimulate another.

Flashcard 59 Q: What are interferons?

A: Cytokines produced in response to infection.

Flashcard 60 Q: What are colony-stimulating factors?

A: Cytokines that stimulate maturation of white blood cells in bone marrow.

Flashcard 61 Q: What are tumor necrosis factors?

A: Cytokines that stimulate inflammatory responses.