Host Response to Viral Infections Flashcards
innate immune system
neither antigen specific nor does it have memory, provides a critical line of first defense against viral infections
skin defenses
keratin (mechanical barrier), low pH, presence of fatty acids, dryness
mucous membranes defenses
virucidal proteins
GI tract defenses
mucous membranes, acidity of the stomach, alkalinity of the intestine, lipolytic activity of bile, proteolytic activity of pancreatic enzymes, IgA
respiratory tract defenses
mucocilliary blanket, temperature gradient, NK cells
mucocilliary blanket
layer of mucus produced by goblet cells, continuous beating of cillia
temperature gradient
nasal passages- 33ºC (rhinovirus)
alveoli- 37ºC (influenza virus)
natural killer cells
early, non-specific resistance against viral infection. granules contain perforins and granzymes. mediate apoptosis in infected cells
PRRs
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
immunopathology
damaging effects to the host in the fight of the viral infection
interferons
group of cytokines that are secreted by somatic cells in response to viral infections and stimuli. orally inactive and should be given parenteral route
type I IFN
- 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
IFN-alpha
leukocyte interferon, non host specific
IFN-beta
fibroblast interferon, host species-specific
autocrine
infected cell secretes IFN that acts on itself; triggers apoptosis
paracrine
infected cell secreted IFN that acts on adjacent cells; inhibiting viral replication
type II IFN
IFN-gamma
IFN-gamma
immunoregulatory, produced by antigen stimulated T cells and NK cells, liable at pH2, host specific
type III IFN
IFN-lambda 1,2,3
recently discovered, expressed in response to viral infection and activation of TLRs
adaptive immunity
cellular: T lymphocytes
humoral: B lymphocytes
what antigens elicit a cell mediated immune response (CMI)
internal viral antigens
what antigens elicit a humoral immune response
surface antigens
do viral infections provoke granulocytosis?
no
opsonization
coating of virions with antibodies so they can be recognized and phagocytosed by macrophages and some neutrophils
clumping of viruses
reduces the number of viral particles available for cell division
bound= not free= no infection
chemotaxis
attracting macrophages and neutrophils
lysis
rupturing of membranes of foreign cells/pathogens
agglutination
clustering and binding of pathogens together (sticking)
ADCC
antibodies bind to viral antigens expressed on host cell surface, host cells is then destroyed by complement mediated cytolysis or phagocytosis
complement mediated cytolysis
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
