Host Response to Viral Infections

Question 1

innate immune system

Answer 1

neither antigen specific nor does it have memory, provides a critical line of first defense against viral infections

Question 2

skin defenses

Answer 2

keratin (mechanical barrier), low pH, presence of fatty acids, dryness

Question 3

mucous membranes defenses

Answer 3

virucidal proteins

Question 4

GI tract defenses

Answer 4

mucous membranes, acidity of the stomach, alkalinity of the intestine, lipolytic activity of bile, proteolytic activity of pancreatic enzymes, IgA

Question 5

respiratory tract defenses

Answer 5

mucocilliary blanket, temperature gradient, NK cells

Question 6

mucocilliary blanket

Answer 6

layer of mucus produced by goblet cells, continuous beating of cillia

Question 7

temperature gradient

Answer 7

nasal passages- 33ºC (rhinovirus)

alveoli- 37ºC (influenza virus)

Question 8

natural killer cells

Answer 8

early, non-specific resistance against viral infection. granules contain perforins and granzymes. mediate apoptosis in infected cells

Question 9

PRRs

Answer 9

pattern recognition receptors: ex. TLRs. the immune system can react when a PRR is bound by a PAMP. causes a release in cytokines, activation of phagocytic cells, endothelial production of inflammatory mediators, and cell surface adhesion molecule expression

Question 10

immunopathology

Answer 10

damaging effects to the host in the fight of the viral infection

Question 11

interferons

Answer 11

group of cytokines that are secreted by somatic cells in response to viral infections and stimuli. orally inactive and should be given parenteral route

Question 12

type I IFN

Answer 12

• IFNalpha
• IFNbeta
• inhibit virus replication by activation of RNAase-L which degrades viral RNA, induces Mx protein which acts as a net and traps virus, induces synthesis of protein kinase R (PKR) which prevents initiation of translation of viral RNA

Question 13

IFN-alpha

Answer 13

leukocyte interferon, non host specific

Question 14

IFN-beta

Answer 14

fibroblast interferon, host species-specific

Question 15

autocrine

Answer 15

infected cell secretes IFN that acts on itself; triggers apoptosis

Question 16

paracrine

Answer 16

infected cell secreted IFN that acts on adjacent cells; inhibiting viral replication

Question 17

type II IFN

Answer 17

IFN-gamma

Question 18

IFN-gamma

Answer 18

immunoregulatory, produced by antigen stimulated T cells and NK cells, liable at pH2, host specific

Question 19

type III IFN

Answer 19

IFN-lambda 1,2,3

recently discovered, expressed in response to viral infection and activation of TLRs

Question 20

adaptive immunity

Answer 20

cellular: T lymphocytes
humoral: B lymphocytes

Question 21

what antigens elicit a cell mediated immune response (CMI)

Answer 21

internal viral antigens

Question 22

what antigens elicit a humoral immune response

Answer 22

surface antigens

Question 23

do viral infections provoke granulocytosis?

Answer 23

no

Question 24

opsonization

Answer 24

coating of virions with antibodies so they can be recognized and phagocytosed by macrophages and some neutrophils

Question 25

clumping of viruses

Answer 25

reduces the number of viral particles available for cell division bound= not free= no infection

Question 26

chemotaxis

Answer 26

attracting macrophages and neutrophils

Question 27

lysis

Answer 27

rupturing of membranes of foreign cells/pathogens

Question 28

agglutination

Answer 28

clustering and binding of pathogens together (sticking)

Question 29

ADCC

Answer 29

antibodies bind to viral antigens expressed on host cell surface, host cells is then destroyed by complement mediated cytolysis or phagocytosis

Question 30

complement mediated cytolysis

Answer 30

Abs bind to Ags on target cell, NK cells CD16 Fc receptors recognize cell-bound antibodies, cross-linking of CD16 triggers degranulation of NK cells, infected cell dies