Immune response to infection (22)

Question 1

What are the general steps of the immune response to infection?

Answer 1

• microbial detection
• innate immune response
• adaptive immune response
• memory response

Question 2

What are the characteristics of innate immunity?

Answer 2

• fast acting, first line of defence, germline encoded receptors
• physical barriers: skin, mucous, epithelial cells
• humoral: complement, lectins, pentraxins, antimicrobial peptides
• cellular: neutrophils, macrophages, dendritic cells, NK cells (all phagocytes)

Question 3

What are the characteristics of adaptive immunity?

Answer 3

• slower but long-lasting, variable receptors that mature over time (DNA recombination)
• humoral: antibodies (immunoglobulins)
• cellular: cytotoxic T-cells, T helper cells, T regulatory cells, B lymphocytes and plasma cells

Question 4

Who are the first responders?

Answer 4

neutrophils, followed by macrophages

Question 5

What are the consequences of uncontrolled activities of phagocytes?

Answer 5

• granulomas
• excessive inflammation and inappropriate adaptive immunity
• tissue damage

Question 6

What cytokine do T-lymphocytes produce in response to the mix of cytokines produced by macrophages?

Answer 6

interferon gamma (IFN-y)- such a potent cytokine that it leads to expression of a large number of genes, which have direct antiviral activities e.g. inhibitors of protein translation

Question 7

What cells kill virus-infected cells in order to remove viral replicative niches?

Answer 7

cytotoxic T-lymphocytes and NK cells

host cells infected w/intracellular bacteria also undergo forms of cell death

Question 8

What cells become activated and present antigens in combination with MHC-1/MHC-2 to T cells?

Answer 8

macrophages and dendritic cells

Question 9

How can we broadly classify T cell functions?

Answer 9

• Phagocyte activation: enhanced killing of pathogens and increase inflammation
• Direct killing of infected cells: removal of replicative niches
• B cell activation: antibody production and affinity maturation
• Innate lymphoid cells: type of early responder (independent of MHC, innate)

Question 10

What cytokines do Th1 cells produce and what are the principal target cells?

Answer 10

IFN-y

activates macrophages- kill intracellular pathogens

Question 11

What cytokines do Th2 cells produce and what are the principal target cells?

Answer 11

IL-4, IL-5, IL-13

eosinophil and mast cell activation- against Helminth infection

Question 12

What cytokines do Th17 cells produce and what are the principal target cells?

Answer 12

IL-17, IL-22

activate neutrophils to tackle fungal infection

Question 13

How is communication mediated between immune cells once resting cells detect microbial ligands?

Answer 13

resting/naive phagocyte detects ligands present in pathogens–> produce proteins/cytokines- interleukins, interferons etc…–> help communicate, signalling to same cell and neighbouring cells–> ‘activated’ host cells