Innate & adaptive immunity

Question 1

List and describe the features of the innate immune system.

Answer 1

• Surface barriers: skin, mucous membranes, reflexes, condition of openings (e.g. acidic, lysozymes)
• Internal defences: fever, inflammation, phagocytes, NK cells [recognise non-self antigens on surface of microbes], antimicrobial proteins like defensin

Question 2

List and describe the features of the adaptive immune system.

Answer 2

• humoral immunity: B cells -> plasma cells -> Ab

- Cellular immunity: (cytotoxic) T cells > intracellular invaders

Question 3

How is the innate system stimulated.

Answer 3

PAMPs: pathogen-associated molecular patterns
DAMPs: damage-associated molecular patterns

Question 4

Why does the innate system lack specificity?

Answer 4

because has no memory and does not stimulate a specific response to foreign antigen. But it discriminates self and non-self

Question 5

List the cardinal signs of inflammation.

Answer 5

• pain
• redness
• immobility
• swelling
• heat

Question 6

In an inflammatory response what do cytokines, chemokines do?

Answer 6

inflammatory mediators

• Cytokines: (proteins released from cells) affect other cells
• Chemokines: (proteins released by cells) to attract other cells to the area

Question 7

How is the adaptive system stimulated and what makes it so specific?

Answer 7

Stimulated by innate system when it’s been breached: message delivered by DC & macrophages. Specific bc has memory that can make specific antibodies for specific pathogen

Question 8

What stimulates TLR3? If Toll-like receptor 3 (TLR3) is stimulated what is the outcome?

Answer 8

TLR3 (toll-like receptor 3) is stimulated when it detects dsRNA in the cytoplasm.
=> stimulates nucleus to turn on genes & make interferons a&B (antivirals)

Question 9

Which TLRs are stimulated by bacterial proteins?*

Answer 9

TLR1 & TLR6*

Question 10

Where are the NOD-like receptors located & function? (nucleotide binding oligomerization-like receptors)

Answer 10

in cytocol of cells bc specific for intracellulr pathogens. Activated by peptidoglycan, RNA, toxins, flagellin & release pro-inflammatory cytokines

Question 11

Describe the two mechanisms by which NK cells are activated.

Answer 11

• missing self hypothesis: activation and inhibitory receptors detect a lack of expression of MHC class 1 on cells
• Antibody dependent cell mediated cytotoxicity (ADCC): NK’s Fc receptor binds to Fc part of antibodies which are attached onto cells = kill these cells

Question 12

What do Dendritic cells and macrophages do? Are they part of the innate or adaptive immune systems?

Answer 12

• Antigen presenting cells of innate system.

- phagocytise antigen & present to T helper cells in lymph node via MHC II

Question 13

What are the down stream effects of an antibody binding to an antigen?

Answer 13

• *trigger phagocytosis (opinisation)
• activate complement => lysis of bacteria
• Neutralise virus & toxins => prevent attachment and penetration in cell
• agglutination

Question 14

role of inflammation

Answer 14

• prevent spread of agent
• dispose debris & pathogens
• tissue repair
• alerts adaptive immune system

Question 15

3 Inflammatory mediators

Answer 15

• cytokines
• chemokines
• acute-phase proteins

Question 16

2 types of pattern recognition receptors and briefly describe what they are

Answer 16

• cellular: phagocytes > promote inflamm. when activated by PAMP/DAMP
• Soluble molecules: in ECF & blood > enhance phagocytosis

Question 17

Why can T cell receptors and antibodies vary even though we have a limited no. of genes?

Answer 17

Somatic cell recombination: multiple gene fragments combined & recombined to form variations in protein binding of antigen