Immune system

Question 1

Role of the skin in immunity?

Answer 1

Barrier formed by keratinized epithelium
Has fatty acids forming a low pH environment
Salty
Natural antibiotics are secreted

Protects us from the vast majority of organisms

Question 2

Airway defences?

Answer 2

Mucin forms a meshwork trapping bacteria and pathogens, with antimicrobial proteins like lysozymes, defensins and lactoferrin, and macrophages

Mucociliary elevator moves foreign pathogens and mucus from lungs back up to the throat where they are swallowed and killed

Question 3

Stranger theory of immunology?

Answer 3

Immune system recognizes and responds to anything foreign

But many foreign particles do not elicit immune responses!

Question 4

Danger theory of immunology?

Answer 4

Tissue or cellular damage or toxin release by pathogens is detected by the immune system

Question 5

Consensus theory of immunology?

Answer 5

Combine both stranger and danger immunology theories, detecting BOTH foreign pathogens and tissue/cellular damage

PAMPs and DAMPs

Question 6

What is innate immunity?

Answer 6

Innate immunity is a generic response, not conferring long-lasting immunity, found in all living organisms, immediate and silent

Recognizes PAMPs and DAMPs

Question 7

Principle molecules of the innate immune system?

Answer 7

Complement - enzymatic pathway principally in the blood, triggering a cascade forming complexes that attack and lyse pathogens

Lysozymes - digestive enzymes secreted in tears and sweat

Type 1 interferons - cytokine released by infected cells to inhibit viral replication

Defensins - antibiotic peptides in tears, sweat and saliva to inhibit synthesis of bacterial cell walls

Question 8

What are PAMPs?

Answer 8

Pathogen associated molecular patterns, secreted by microbes and not found in our own tissues

We have developed receptors for all PAMPs to recognize threat presences

Toll-like receptors, initiating proinflammatory signaling cascades, are expressed by macrophages, dendritic cells and neutrophils

Question 9

What are DAMPs?

Answer 9

Damage Associated Molecular Patterns, molecules released from damaged tissues, basically essential cell components that would never be found outside cell compartment unless cell is damaged

Question 10

What do neutrophils and macrophages do

Answer 10

Neutrophils are mobilized to site of infection as first wave of leukocytes, phagocytosing microbes

Macrophages patrol and phagocytose invading pathogens and cellular debris to keep tissue homeostasis

Question 11

What is adaptive immunity?

Answer 11

A stronger, much more focused immune response generating immunological memory

Recognizes pathogen based on signature antigens

Exploited in vaccinations

Involves dendritic cells (linking innate and adaptive) and T/B lymphocytes

Question 12

What are dendritic cells?

Answer 12

Sentinels of the immune system at all peripheral sites, forming meshworks trapping and recognizing invading pathogens

Filter lymphatic/interstitial fluid for pathogens

Antigen-presenting cells via TLRs recognizing PAMPs, initiating the adaptive immune response by activating T/B cells

Question 13

How do B cells bind to antigens?

Answer 13

Dendritic cells package antigens into iccosomes, B cells bind to iccosomes

Question 14

How do T cells bind to antigens?

Answer 14

Receptors are evolved to target peptides displayed in association with MHC on dendritic cells, each MHC can bind to different types of antigen proteins

Question 15

Functions of T cells

Answer 15

CD4 T-helper cells activate B cell humoral responses via cytokines to combat extracellular pathogens (MHC Class 2)

CD8 cytotoxic cells recognize and kill cells harboring intracellular pathogens (MHC Class 1), using granzymes and perforins to lyse infected cells

Question 16

Functions of B cells

Answer 16

Makes antibodies (immunoglobulins)
Encode a B cell receptor which is a membrane tethered antibody
Each B cell produces immunoglobulins specific for only one antigen

Question 17

Types of immunoglobulins

Answer 17

Depend on what cytokines are produced by CD4 T-helper cells

IgM - early stages of infection, lots of binding sites making it very effective in antigen-binding, recruits complement system in the beginnings of adaptive response

IgG - neutralizes pathogens directly

IgA - IgG but in oral/nasal cavity and mucosal sites of the body to neutralize pathogens in mucin layers of mucosal sites

IgE - anti-parasite immunity, involved in allergy and asthma as it causes mast cell degranulation