ICS- Immunlogy

Question 1

List the humoral components of the immune system

Answer 1

• coagulation system
• complement system
• fibrinolytic system
• kinin system

Question 2

how does the coagulation system function as a humoral component of the immune system?

Answer 2

Clots act to immobilize microorganisms and prevent entry into blood and lymph

Question 3

how does the complement system function as a humoral component of the immune system?

Answer 3

it enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism

Question 4

how does the fibrinolytic system function as a humoral component of the immune system?

Answer 4

it decomposes the clot when it’s no longer required to promote wound healing

Question 5

how does the kinin system function as a humoral component of the immune system?

Answer 5

it widens blood vessel lumens and increases capillary permeability thus increasing supply of soluble and cellular material to the site of infection

Question 6

what is the function of neutrophils?

Answer 6

• first responders to infection
• phagocytose bacteria
• most abundant (70%)

Question 7

what is the function of lymphocytes?

Answer 7

B-lymphocytes: produce antibodies, differentiate into plasma cells or memory B cells
T- lymphocytes: cell mediated immunity

Question 8

what is the function of eosinophils?

Answer 8

they are involved in allergic reactions and defence against parasites

Question 9

what is the function of basophils?

Answer 9

they mediate allergic and inflammatory responses by releasing histamine and other mediators

Question 10

what is the function of monocytes?

Answer 10

• precursors to macrophages and dendritic cells
• phagocytose pathogens
• present antigens
• produce cytokines

Question 11

what is the complement system?

Answer 11

it is a series of protein activations that help the body’s immune system remove foreign particles and pathogens. it forms a part of the innate immune system.

Question 12

where do the plasma proteins involved in the complement cascade come from?

Answer 12

the liver

Question 13

what are the activation pathways involved in the complement cascade?

Answer 13

• Classical
• Lectin
• Alternative

Question 14

describe the classical activation pathway of the complement cascade

Answer 14

Antibody (IgG & IgM) binds to antigen on a microbe which causes C3 to be converted into C3a and C3b.

Question 15

Describe the Lectin activation pathway of the complement cascade

Answer 15

Mannose-binding Lectin (MBL) binds to mannose carbohydrate found on pathogen surfaces. this converts C3 into C3a and C3b.

Question 16

Describe the Alternative pathway of the complement cascade

Answer 16

It is activated by bacterial endotoxin, a lipopolysaccharide present on the outer membrane of gram negative bacteria. this results in spontaneous hydrolysis of C3 into C3a and C3b.

C3b combines with other factors to form C3 convertase which converts C3 into C3a and C3b.

Question 17

what is the inflammatory boost mode of action involved in the complement cascade?

Answer 17

C3a and C5a attract more leukocytes to the site of infection

Question 18

what is the opsonisation mode of action involved in the complement cascade?

Answer 18

when C3b binds to pathogens to promote phagocytosis

Question 19

what is the direct lysis mode of action onvolved in the complement cascade?

Answer 19

When C5b forms the membrane attack complex (MAC) which creates pores in the pathogen membrane, leading to cell lysis.

Question 20

Through which ways does the protein C3a help fight infection?

Answer 20

C3a attracts more leukocytes to the site of infection. this is called an inflammatory boost

Question 21

Through which ways does the protein C3b help fight infection?

Answer 21

• C3b combines with other factors to form C3 convertase which converts more C3 into C3a and C3b (Self-amplification loop)
• C3b binds to pathogens to promote phagocytosis (opsonisation)
• C3b converts C5 into C5a and C5b which also cause inflammatory boost and produce the MAC respectively.

Question 22

Through which ways does the protein C5a help fight infection?

Answer 22

C5a attracts more leukocytes to the site of infection (Inflammatory boost)

Question 23

Through which ways does the protein C5b help fight infection?

Answer 23

C5b forms the membrane attack complex (MAC) which forms pores in the membranes of the pathogens, leading to cell lysis

Question 24

Describe IgM’s structure

Answer 24

• It’s produced early in immune response
• has low affinity, high avidity
• activates the complement cascade
• it’s a monomer (B-cell receptor) or pentamer (agglutination, opsonisation); key in the primary immune response.

Question 25

Describe IgA’s structure

Answer 25

• Mucosal immunity (Gut and lung)
• found on mucosal surfaces
• Secreted as a dimer joined by a J chain

Question 26

Describe IgG’s structure

Answer 26

• > 80% circulating antibodies are IgG
• Used to diagnose pas/ persistent infections