Unit 6- Immunity

Question 1

What forms the body’s first physical line of defense against microbial invasion?

Answer 1

• Skin
• Mucous Membranes

The skin and mucous membranes create barriers that resist microbial growth.

Question 2

What is keratinization in the context of skin defense?

Answer 2

The outer layer of the skin consists of tightly packed, dead epithelial cells filled with keratin

This creates a dry, inhospitable surface that resists microbial growth.

Question 3

What role does mucus production play in mucous membranes?

Answer 3

Traps microbes and debris, preventing them from reaching underlying tissues

Mucous membranes line the respiratory, digestive, and urogenital tracts.

Question 4

What is the purpose of continuous cell shedding in skin and mucosal epithelial cells?

Answer 4

Sloughs off microbes attached to them before they can colonize or invade deeper tissues

This process helps maintain a barrier against infection.

Question 5

What is the mucociliary escalator?

Answer 5

Cilia in the respiratory epithelium move mucus and trapped particles upward toward the throat

This mechanism helps clear microbes from the respiratory tract.

Question 6

What is peristalsis in the intestinal tract?

Answer 6

Wave-like muscle contractions that propel contents toward the anus

This process helps clear microbes and prevent their buildup.

Question 7

What is the role of salt in skin defense?

Answer 7

Creates a hypertonic environment that dehydrates and kills most microbes

This occurs through the evaporation of sweat.

Question 8

What is lysozyme and where is it found?

Answer 8

An enzyme that breaks down peptidoglycan in bacterial cell walls

Found in tears, saliva, mucus, and phagocytic cells.

Question 9

What are defensins?

Answer 9

Short, positively charged peptides that disrupt microbial membranes

They insert into membranes and form pores, causing microbial death.

Question 10

What is nutritional immunity?

Answer 10

The body restricts microbial growth by withholding essential nutrients, especially iron

Lactoferrin and transferrin bind free iron, making it unavailable to microbes.

Question 11

What is the role of normal microbiota in host defense?

Answer 11

• Competitive exclusion
• Antimicrobial compound production
• Immune system training

These commensal microbes protect the host from pathogens.

Question 12

What can cause dysbiosis?

Answer 12

Disturbance of microbiota balance

This can lead to the proliferation of opportunistic pathogens.

Question 13

What are PAMPs?

Answer 13

Molecules unique to microbes but absent in host cells

Examples include peptidoglycan, LPS, and flagellin.

Question 14

What are DAMPs?

Answer 14

Molecules released by damaged or dying host cells

Examples include ATP, uric acid, and heat shock proteins.

Question 15

What do cell surface PRRs detect?

Answer 15

Extracellular microbes or components like LPS and peptidoglycan

Examples include TLR2, TLR4, and TLR5.

Question 16

What do endosomal PRRs detect?

Answer 16

Internalized microbes or viral nucleic acids after phagocytosis/endocytosis

Examples include TLR3, TLR7, TLR8, and TLR9.

Question 17

What are the consequences of PRR activation?

Answer 17

• Cytokine release
• Chemokine release
• Type I interferon production

These responses promote inflammation and recruit immune cells.

Question 18

What are the three major functions of the complement system?

Answer 18

• Opsonization
• Inflammatory response/recruitment
• Lysis of foreign cells

These functions help eliminate pathogens.

Question 19

Compare neutrophils and macrophages as phagocytic cells.

Answer 19

• Neutrophils: Short-lived, first responders, rapid phagocytosis
• Macrophages: Long-lived, later responders, coordinate immune response

Each has distinct roles in the immune response.

Question 20

What are the key steps of phagocytosis?

Answer 20

• Chemotaxis
• Recognition & Attachment
• Engulfment
• Phagosome-Lysosome Fusion
• Digestion
• Exocytosis

These steps detail how phagocytes eliminate pathogens.

Question 21

What are the classical signs of inflammation?

Answer 21

• Redness (rubor)
• Heat (calor)
• Swelling (tumor)
• Pain (dolor)

These signs result from increased blood flow and vascular permeability.

Question 22

What is the difference between apoptosis and pyroptosis?

Answer 22

• Apoptosis: Programmed, non-inflammatory cell death
• Pyroptosis: Inflammatory cell death triggered by infection

Pyroptosis releases cytokines and alerts nearby immune cells.

Question 23

Identify a strategy pathogens use to evade phagocytosis.

Answer 23

• Capsule formation
• Mimicking host molecules
• Destroying complement components
• Preventing phagosome–lysosome fusion
• Escaping phagosome into cytoplasm

These strategies help pathogens avoid immune detection.

Question 24

What are the four defining characteristics of adaptive immunity?

Answer 24

• Specificity
• Diversity
• Memory
• Self vs. nonself discrimination

These characteristics distinguish adaptive immunity from innate immunity.

Question 25

How do **B cells** and **T cells** recognize antigens?

Answer 25

* B cells: Bind free antigens via B cell receptors * T cells: Recognize processed antigens presented on MHC molecules ## Footnote This difference is crucial for their respective immune functions.

Question 26

What is the role of **MHC Class I**?

Answer 26

Presents intracellular antigens to CD8⁺ cytotoxic T cells ## Footnote Found on all nucleated cells.

Question 27

What is the role of **MHC Class II**?

Answer 27

Presents extracellular antigens to CD4⁺ helper T cells ## Footnote Found on professional antigen-presenting cells.

Question 28

What is required for **lymphocyte activation**?

Answer 28

* Signal 1: Antigen recognition * Signal 2: Co-stimulatory signal ## Footnote This two-signal requirement prevents autoimmunity.

Question 29

What happens during **B cell activation**?

Answer 29

* Antigen binding * Internalization and presentation * Helper T cell interaction * Clonal expansion * Differentiation into plasma and memory B cells ## Footnote This process leads to antibody production.

Question 30

How do **dendritic cells** link innate and adaptive immunity?

Answer 30

Detect danger signals and present antigens on MHC molecules to T cells ## Footnote This ensures adaptive immunity is activated only when there's a real threat.

Question 31

What distinguishes **primary** from **secondary immune responses**?

Answer 31

* Primary: 10–14 days lag, mainly IgM, moderate antibody levels * Secondary: 2–3 days lag, mainly IgG, 10–100× higher antibody levels ## Footnote Secondary responses are faster and more robust due to memory cells.

Question 32

What are the properties of **immunological memory**?

Answer 32

* Longevity * Increased numbers * Primed state * Enhanced quality ## Footnote These properties are the basis for effective vaccination.

Question 33

What are the **four ways to acquire immunity**?

Answer 33

* Active immunity (natural) * Active immunity (artificial) * Passive immunity (natural) * Passive immunity (artificial) ## Footnote Each method contributes to the immune system's ability to respond to pathogens.

Question 34

What is **herd immunity**?

Answer 34

Protects even non-immunized individuals if enough of the population is vaccinated ## Footnote This concept is crucial for controlling infectious diseases.

Question 35

What must vaccines be in terms of **safety and effectiveness**?

Answer 35

Safe for healthy individuals with minimal side effects ## Footnote They should prevent disease and ideally prevent colonization.

Question 36

What are **attenuated vaccines**?

Answer 36

Live, weakened vaccines that can colonize the body without causing disease ## Footnote Often require a single dose for effective immunity.

Question 37

What is the purpose of **vaccination**?

Answer 37

* Prevent disease but may not prevent colonization * Sterilizing immunity: prevents infection and transmission * Herd Immunity: protects even non-immunized individuals if enough of the population is vaccinated ## Footnote Example: 2006 pneumococcal conjugate vaccine in the UK reduced infections even in unvaccinated populations.

Question 38

What are the **two main types of vaccines**?

Answer 38

* Attenuated (live, weakened) vaccines * Inactivated (killed/subunit) vaccines ## Footnote Attenuated vaccines can colonize the body without causing disease, while inactivated vaccines contain only part of the pathogen.

Question 39

What are the characteristics of **attenuated vaccines**?

Answer 39

* Can colonize the body without causing disease * Often single dose confers protection * Risks: possible reversion to virulent form, issues for immunocompromised individuals ## Footnote These vaccines are effective but carry some risks.

Question 40

What are the characteristics of **inactivated vaccines**?

Answer 40

* Contain only part of the pathogen (protein, sugar, toxin) * Safe for immunocompromised individuals * Often require multiple doses/boosters * Adjuvants help stimulate the immune system ## Footnote Adjuvants, like alum, stimulate the innate immune response.

Question 41

What is an **immunogen**?

Answer 41

The component to generate immunity ## Footnote It is a crucial part of vaccine composition.

Question 42

What is an **adjuvant**?

Answer 42

Stimulates innate immune response and maintains antigen at injection site ## Footnote Adjuvants are often included in vaccines to enhance their effectiveness.

Question 43

What are the historical examples of vaccines mentioned?

Answer 43

* Polio * Measles ## Footnote These examples illustrate the impact and importance of vaccination in public health.

Question 44

What are the two types of **polio vaccines**?

Answer 44

* Inactivated polio vaccine (Salk) * Live attenuated polio vaccine (Sabin) ## Footnote The Salk vaccine protects individuals but does not provide sterilizing immunity, while the Sabin vaccine does.

Question 45

True or false: The **measles vaccine** has prevented millions of deaths.

Answer 45

TRUE ## Footnote It is estimated to have prevented around 60 million deaths over 25 years.

Question 46

What was the impact of **Andrew Wakefield's fraudulent paper**?

Answer 46

Caused decades of harm by falsely linking MMR vaccine to autism ## Footnote This misinformation significantly affected public perception of vaccines.

Question 47

What is the target identified for **COVID-19 vaccines**?

Answer 47

SARS-CoV-2 spike protein ## Footnote This target is crucial for the development of effective vaccines.

Question 48

Name the **three platforms** used for COVID-19 vaccines.

Answer 48

* Oxford-AstraZeneca: viral vector vaccine * mRNA vaccines: quick adaptation, high efficacy * Novavax: protein-based vaccine ## Footnote These platforms highlight the diversity in vaccine development strategies.

Question 49

What considerations are there for **young children** regarding vaccines?

Answer 49

Immune system 'learning mode'; may need specific formulations ## Footnote This affects how vaccines are designed for different age groups.

Question 50

What does **seronegative** mean?

Answer 50

No antibodies → no prior exposure ## Footnote This term is used in immunological testing.

Question 51

What does **seropositive** indicate?

Answer 51

Antibodies present → prior exposure or vaccination ## Footnote This status is important for understanding immunity.

Question 52

What are **polyclonal antibodies**?

Answer 52

Many targets, robust protection, used for passive immunity ## Footnote These antibodies are derived from multiple B cell lineages.

Question 53

What are **monoclonal antibodies**?

Answer 53

Single target, precise, less robust, can be recombinantly produced ## Footnote These antibodies are engineered to target specific antigens.

Question 54

What is the goal of the **EPIC (Emerging and Pandemic Infections Consortium)**?

Answer 54

Integrate expertise across multiple fields ## Footnote This consortium focuses on addressing infectious diseases through collaborative research.

Question 55

What are the **four pillars** of EPIC?

Answer 55

* Transformative research * Innovative infrastructure * Training & talent * Knowledge translation ## Footnote These pillars guide the consortium's efforts in tackling emerging infections.