Immunology: Effector Mechanisms of Humoral Responses

Question 1

Antibodies mediate destruction of extracellular microorganisms by

Answer 1

• Neutralization of bacterial toxins, viruses, and bacteria
• Opsonization to enhance phagocytosis of bacteria by macrophages and neutrophils
• Activation of complement

Question 2

Antibodies can activate a variety of accessory cells expressing

Answer 2

Fc receptors

Question 3

Fc receptors recognize

Answer 3

• IgG
• IgA
• IgE
• NOT IgM

Question 4

Which cells bind to IgE via Fc

Answer 4

• NK cells
• Mast cells
• Basophils
• Activated eosinophils

Question 5

Antibody-dependent cell-mediated cytotoxicity (ADCC) is mediated by ___ which

Answer 5

NK cells which kill IgG coated target cells

Question 6

IgE mediated activation of accessory cells plays a role in

Answer 6

Resistance to parasite infections

Question 7

Pathways of complement system

Answer 7

• Classical
• Alternate
• Lectin

Question 8

Classical pathway is initiated by

Answer 8

Antigen-antibody complexes (IgM or IgG)

Question 9

Alternate pathway is activated

Answer 9

Directly by surfaces of infectious organisms/cell walls of gram-negative bacteria and yeasts

Question 10

Lectin pathway is activated by binding of

Answer 10

mannose binding lectin to microbe

Question 11

All pathways of complement converge and utilize ___ to form

Answer 11

C3 protein to form enzymes that initiate the common terminal pathway –> formation of membrane attack complex

Question 12

Biologic functions of complement system

Answer 12

• Cytolysis
• Opsonization of organisms and immune complexes for phagocytosis
• Production of inflammation
• Enhancement of humoral immune response
• Solubilization and clearance of immune complexes

Question 13

Most serum complement proteins are synthesized by

Answer 13

Liver and macrophages

Question 14

Most abundant protein in complement serum

Answer 14

C3

Question 15

Best C3b receptor is

Answer 15

CR1

Question 16

CR1 is expressed on

Answer 16

• Phagocytic cells

- Erythrocytes

Question 17

Individuals deficient in C3 suffer from

Answer 17

recurrent infections with pyogenic and gram-negative bacteria

Question 18

Deficiencies in C1, C4 and C2

Answer 18

• Autoimmune diseases in patients with syndromes that resemble systemic lupus erythematosus (SLE)
• Increased susceptibility to bacterial infections

Question 19

Anaphylatoxins

Answer 19

Increase vascular permeability and recruit inflammatory cells at site of antigen deposition

Question 20

C5a is a

Answer 20

Chemattractant and activator of neutophils

Question 21

Hereditary angioneurotic edema

Answer 21

Lack of inhibitor of C1 esterase –> action of C1 on C4 and C2 is uncontrolled –> Increase in vasoactive peptides –> patients suffer from edema

Question 22

Proteins that inhibit inadvertent activation of complement

Answer 22

• Decay accelerating factor

- CD59

Question 23

CD 59

Answer 23

Prevents formation of MAC

Question 24

Paroxysmal nocturnal hemoglobulinuria

Answer 24

Deficiency in DAF or CD59 –> increased sensitivity to complement-mediated lysis of erythrocytes