V3 Flashcards
What are the host’s defence mechanisms against viral infections?
- non-specific defence mechanisms
- the immune system (humoral and cell-mediated responses as well as interferon)
Name 5 non-specific factors involved in Immunity
- barriers
- fever and inflammation
- nutritional status
- hormones
- genetic factors
What are 2 barriers in non-specific immunity? (and give examples)
- Physical: Skin, Epithelial cilia in respiratory tract, Mucous membranes.
- Chemical: Low pH in stomach (HCl), Lysozyme in saliva, Lacrimal fluid.
What does fever and inflammation do?
Limit replication of viruses
What is the effect of nutritional status on non-specific immunity?
Poor nutrition may exacerbate the severity of some
infections
What is the effect of hormones on non-specific immunity?
Treatment with steroids may exacerbate the severity of herpes simplex and varicella zoster infections.
What is the effect of genetic factors on non-specific immunity?
Resistance or slower disease progression with mutations of CCR5 co-receptor in HIV infection.
What are 3 types of immune responses?
- Natural protection (barriers and chemicals).
- Innate (non-adaptive).
- Acquired (adaptive).
Describe what happens during the first line of defence (natural protection)
There are non-specific physical and chemical defences as well as expulsion (coughing etc.) that keeps foreign bodies out.
Explain what happens during the second line of defence (non-adaptive)?
- Recruits immune cells to the site of infection or inflammation through production of cytokines.
- Activate complement cascade to promote clearance of dead cells or antibody complexes.
- Specialized WBC’s identify and remove foreign substances from body sites.
- Activate the adaptive immune system through antigen presentation.
What are MHCs?
Group of genes that code for protein found on cell surface that help immune system recognise foreign substances.
What is the function of MHCs?
Antigen recognition and development of humoral and cell mediated response
What is the difference between MHC I and MHC II?
- MHC I: All nucleated cells; Present peptide antigen to NK cells
- MHC II: Only antigen producing cells; Present peptide antigen to t-helper cells
How do NK cells work?
- Virally induced MHC class I down regulation triggers NK cells to kill the infected cells
- Recognize infected cells coated with antiviral antibodies using Fc receptors, and kill them through Antibody Dependent Cell-Mediated Cytotoxicity (ADCC).
- Produce increased amounts of interferons and binds IFN-R to prevent production of virus.
What do interferons do?
- Bind to receptors on infected or uninfected cells to prevent further spread of the virus
- Bind to IFN-R: Inhibits synthesis of viral proteins, increases expression of MHC class I molecules
- increases the effectiveness of NK cells
