immunity and response to infection

Question 1

pyrogens

Answer 1

peptides secreted by leukocytes and act on hypothalamus inducing fever which inhibit iron uptake by bacteria

Question 2

interferons

Answer 2

proteins that modulate immune response and act as antiviral agents

Question 3

complement proteins

Answer 3

plasma proteins that destroy cells

Question 4

phagocytes

Answer 4

immune cells that can digest foreign antigens

Question 5

neutrophils

Answer 5

type of WBC that are the first line of action at site of infection

Question 6

monocytes

Answer 6

monocellular phagocytes in the blood, differentiate into macrophages in tissues

Question 7

microglia

Answer 7

CNS resident and help maintain homeostasis

Question 8

dendritic cells

Answer 8

derived from monocytes - found in tissues like lymph

Question 9

antimicrobial function of phagocytes

Answer 9

phagocytic cell is attracted to and recognises microbes as being foreign via surface receptors
it extends filopodia engulfing the microbe and phagosomes begin to form
once contained in a phagosome, fusion with a digestive enzyme containing lysosome occurs

Question 10

chemotaxis

Answer 10

chemical attractants from invading bacteria and tissue leukocytes attract local neutrophils and monocytes from blood stream

Question 11

diapedesis

Answer 11

mast cells and basophils release histamine making the blood vessel permeable and allowing cells through

Question 12

antigens

Answer 12

usually high MW substances and contain epitopes

Question 13

haptens

Answer 13

carrier molecule protein that binds to low MW compounds and illicit an immune response
ex: penicillin can act as a hapten in some patients which can lead to severe reaction called anaphylaxis

Question 14

opsonisation

Answer 14

the coating of foreign antigens by antibodies making them attractive to neutrophils (natural killer cells and macrophages)

Question 15

opsonin

Answer 15

protein which promotes opsonisation

Question 16

neutralisation

Answer 16

bacterial toxins are neutralised by antibodies e.g. diptheria, tetanus, botulinumtoxin

Question 17

complement cascade

Answer 17

• The classical pathway: C1 recognises microbial surface
• The lectin pathway: initiated by soluble carbohydrate binding proteins that bind to carbohydrate structures on microbial surfaces
• The alternative pathway: initiated by spontaneous hydrolysis and activation of C3
• C3 convertase cleaves C3 into C3b and C3a (peptide inducing inflammation)
  C3b binds to microbial surfaces and acts as an opsonin
• C5 convertase cleaves C5 into C5a and C5b
• C5b initiates the interaction to form membrane attack complex (MAC) on the pathogen surface
  -creating a pore in the cell membrane that leads to cell lysis due to osmotic shock

Question 18

B-cells

Answer 18

• plasma B cells produce antibodies
• memory B cells lead secondary immune response
• B-cells are activated when free antigens bind to immunoglobulin (IgM/IgD) receptors on the B-cell surface
• during infection binding of antigens to B or T cells triggers clonal proliferation

Question 19

clonal proliferation

Answer 19

• antigen binds to B-cell via IgR activating it
• T-cell moves to B-cell activates it
• activated B-cell proliferates
• differentiating into antibody producing plasma cells or memory cells

Question 20

helper T-cells

Answer 20

release interleukins and activate macrophages and cytotoxic T-cells (Th1)
they also activate B-cells and help recruit neutrophils and macrophages

Question 21

regulatory T-cells

Answer 21

dampen immune response

Question 22

memory T-cells

Answer 22

increase longevity of immunity

Question 23

cytotoxic T-cells

Answer 23

directly kill infected cells

Question 24

T-cell activation

Answer 24

• class 1 major histocompatibility complex (MHC) proteins activate CD8 + cytotoxic T-cells
• class 2 major histocompatibility complex (MHC) proteins activate CD4 + helper T-cells

Question 25

Th-cell + B-cell activation

Answer 25

• activated Th-cell finds B-cell that recognises its peptide antigen forming an immunological synapse
• Th-cells release cytokines which stimulate further B-cell production of antibodies (IgE)