Host Defenses Flashcards
What is the role of innate immunity?
Early defense
No memory
Many pathogens have resistive mechanisms (parasites)
What is the role of adaptive immunity?
Longer to develop
Antigen specific
Memory Response
Optimal type of immune response for a pathogen
What viruses primarily enter through the skin?
HepB/Papilloma v (minor breaks/cuts)
Rabies (Animal Bites
West Nile Virus (Mosquito bite)
HIV/Hep B/C (injection)
What viruses primarily enter through the ailmentary tract?
(naked viruses can survive bile better)
HSV 1/EBV (mouth)
Hep A/Rotavirus/Poliovirus (GI)
What viruses primarily enter through the Resp Tract??
(Resp tract bugs have trouble surviving in the GI tract) Adenovirus/Rhinovirus (URT, local)
Influenza/RSV (LRT, local)
Measles/mumps/rubella/varicella (local infection, systemic dx)
What viruses primarily enter through the conjunctiva?
Adenovirus/Enterovirus (direct contact)
What are the cellular forms of Innate immunity against viruses?
Inteferon a and B (Type 1 interferon)
Natural Killer Cells
Macrophages
What are the effects of the Interferons?
Produced by virus INFECTED host cells
Inhibit viral replication in surrounding UNINFECTED host cells
Leukocytes => Produce interferon alpha
(Fibroblasts + other non leukocytes produce INF-B)
Activate dendritic cells and macrophages
Activate NK cells
What are the Attributes of Natural Killer Cells?
Lyse Virus infected cells early in virus infection
Some viruses dec prod of MHC1 to avoid lysis by CTLs
NK cells are activated by ABSENCE of MHC 1
NK cells enhanced by the interferons
What kills virus infected cells if MHC1 is present?
Not present?
CD8+ T cells (Cytotoxic Lymphocytes, CTLs)
Natural Killer cells
What is the role of NK cells
Mediate ADCC
Crosslinking of IgG Fc receptors triggers ADCC
Kill via Apoptosis and perforin mediated osmotic death
How can macrophages fight/help Viruses?
Produce TNF-a and NO => interfere with virus replication
Can be infected by viruses( CMV, Ebola, HIV, MEasles, rubella
Traffic to many body sites (FACILLITATES virus spread)
What are the functions of Antibodies?
Prevent virus from binding a target host cell
Opsonize virus (phagocytosis)
Activate compliment (lyse viral
envelopes)
Facilitate ADCC by NK cells
Downreg. expression of viral genes inside infected cells
What are strategies of Evasion of immunity?
Alter anttigen through point mutation
Prevent MHC1 mediated expression of viral peptides
HIV infects/kills CD4+ T cells
What are deletrious effects of the immune response?
Hep B = Liver damage Chronic infection => Immune complex disease Molecular mimicry(viral cells can express proteins similar to normal tissue)
