Introduction to the cells and systems of the immune system

Question 1

how does our immune system distinguish between self/non-self?

Answer 1

•Self molecules (proteins, DNA, lipids, Carbohydrates) are found on our cells/tissues/organs

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•Our immune system as it matures learns to recognise our own ‘self’ molecules and not react – tolerance using “pattern recognition receptors (PRR)

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•In contrast we have evolved mechanisms to specifically recognise bacterial and viral Antigens

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•We have evolved families of cell-surface receptors that can distinguish self and non-self antigens

Question 2

what can occur if our immune system is not behaving as it should?

Answer 2

overreaction = allergies - develops when immune system recognizes a harmless environmental antigen and launches an attack

underreaction = Cancer – immune system fails to recognise cancerous cells as defective or altered

recognizes self - autoimmunity - recognises our own cells and tissues and attacks Type I Diabetes a good example…..

Question 3

Describe the three types of protective immunity in the human body

Answer 3

1. barrier immunity - prevents pathogens from getting into the body i.e. mucus, skin or acidity
2. innate immunity - immediate response to breach in barrier - swelling and redness allows immune cells to reach the site of injury
3. adaptive immunity - delayed response but specific for each pathogen - Tcells, Bcells, antibodies etc.

Question 4

What makes up our first line of immune defense?

Answer 4

• skin
• epithelial lining / rapid turnover of epithelial cells
• commensal bacteria
• cilia
• tears
• peristalsis - continuous movement of food/microbes

Question 5

what are some anti-microbial peptides that are found in our first line of immune defense?

Answer 5

defensins

cathelicidins

histatins

all produced by epithhelial cells and phagocytes - disrupt the membranes of bacteria, fungi, and virus

Question 6

what makes up our innate immunity vs. our adaptive immunity?

Answer 6

Innate (non-specific) immunity

• phagocytes - cells that eat invaders
• secretory (cells that release toxins)
• can broadly distinguish self from non-self
• alarm system
• inflammatory barriers (redness, swelling, heat and pain)

Adaptive (specific) immunity

• B lymphocytes
• T lymphocytes
• antigen specificity
• diversity
• immunological memory
• self/non-self recognition

Question 7

What are the three main priorities of the innate immune system?

Answer 7

Destroy threat by …

1. Engulfs and kills target (Phagocyte and Secretion)
2. Send signals for recruitment
3. Induce Inflammation (HIS15)

Question 8

what do phagocytes do?

Answer 8

engulf bacterium - bacteria killed by toxic oxygen radicals and enzymes like lysozyme (highly acidic)

Question 9

Describe the different types of phagocytic cells

Answer 9

Macrophage/monocytes

• tissue resident macrophages -
  
  • Liver= kupffer cells
  • lung= alveolar macrophages
  • CNS - microglial cells
  • Bone - osteoclasts
• Monocytes circulate in blood- migrate into tissues and then differentiate into macrophages

Dendritic Cells

• tissue residing or circulating
• phagocytose pathogens and present the antigens to T cells
• they are the link between the innate immune system and the adaptive immune system

Neutrophils

• most abundant phagocyte in blood
• quickly migrate to infection
• short life span
• very important in clearing bacterial infections
• then they take up the microorganism to kill it, they too die and release their DNA to entrap the microorganisms and promote danger signals

Question 10

What are the three types of secretory cells?

Answer 10

Mast cells

basophils and

eosinophils

Question 11

what role do mast cells and basophils play in immunity?

Answer 11

They are secretory cells that are resident in many tissues- they are packed ull of dense granules containing toxic substances to kill target pathogens - they also release proteins to trigger an inflammatory response. - these are the main players in asthma

Question 12

What role to eosinophils play in immunity?

Answer 12

they are evolved to protect against helminth infection - once they recognize a worm, they will try to kill it with granules -

Question 13

What cells make up the adaptive immune system?

Answer 13

T cells and B cells

Question 14

are T cells and B cells generalized in function? Or are they antigen specific?

Answer 14

They are antigen specific

Question 15

what role do B cells/lymphocytes play in immunity?

Answer 15

They recognize a single antigen via B cell receptor - antigen receptor - once activated , they make an secrete antibodies that will recognize the antigen that prompted it

Question 16

What are antibodies?

Answer 16

They are proteins made by the B cell- secreted to fight infection - recognizes specific antigen and binds to it - once it does, it promotes neutralisation, clumping or aggregation, and uptake by macrophages

Question 17

What role to T cells/Lymphocytes play in immunity?

Answer 17

T cells also have an antigen receptor on the cell surface (T cell receptor) , but each T cell only recognises a single antigen

two different types of T cells

helper T cells = help B cells become activated

cytotoxic = kill infected cell or altered cells (killer T cell)

Question 18

where is the immune system int he body?

Answer 18

Generally

primary lymphoid organs

• thymus and bone marrow-

Secondary lymphoid organs

• lymph nodes, spleen white pulp, mucosal associated lymphoid tissue-

Question 19

what is the purpose of lymph nodes?

Answer 19

they are specialized to trap antigen-bearing dendritic cells and present to T cells and allow initiation of adaptive immune responses

Question 20

how do cells communicate?

Answer 20

soluble mediators : cytokines and chemokines

cell/cell contact: receptors and co-receptors

Question 21

How do cytokines work?

Answer 21

• Work by binding cell surface receptor and triggering gene expression
• Only cells with receptors specific will respond to a given cytokine

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• IL-1 or TNF: Receptors for these cytokines on many different cell types – therefore wide ranging effects
• IL-2 only acts on T and B cells so receptor only expressed there

Question 22

What are cytokines?

Answer 22

they are small proteins that work to affect the immune response

they stimulate, inhibit, and control growth and maintenance

conceptually, they are similar to hormones but they aren’t produced by one type of tissue. They are produced by barrier cells that interact with the immune system and the immune system itself

cytokines can act locally or systemically

Question 23

What are the different types of cytokines?

Answer 23

interleukins- between leukocytes

• actiators = IL2, IL12
• drive inflammation = TNF, IL1
• inhibitors = IL10
• differentiation = IL23

interferons

• Type 1 (IFN alpha/beta) produced in response to viral infection and act to limit spread and growth
• Type 2 (IFN gamma) important activator of phagocytes

colony stimulating factors

• growth factors and differentiation cytokines (GM-CSF, G-CSF)

chemokines

• act as chemoattractants - to site of infection (IL8)

Question 24

Which immunity rapidly discriminates between self and non-self?

Answer 24

Innate immunity

Question 25

what are the 2 wyas the immune system communicates?

Answer 25

cell-cell contact

or

cytokines

Question 26

what are the primary and secondary lymph organs? What are their functions?

Answer 26

primary lymphoid organs = thymus and bone marrow - mature lymphocytes

secondary lymphoid organs = lymph nodes, spleen white pulp, mucosal assocated lymphoid tissue - provide environment for interaction between lymphoid cells and trapped microorganism