Immune response to infection Flashcards
What part of the immune system do natural killer cells belong to?
Innate immune system.
What are the 4 pathogen niches?
Extracellular(staphylococcus, streptococcus), intracellular but vacuolar(salmonella and chlamydia), surface adherent(E coli) and intracellular but cytosolic (viruses).
What are the first cells to respond to infection?
Neutrophils followed by macrophages.
If macrophages aren’t controlled what can happen?
Formation of granulomas.
What is the macrophage t cell interaction that leads to macrophage activation?
Macrophages releases IL-12. T helper cell responds by releasing IF gamma and this activates macrophage. Macrophage phagocytoses pathogen.
What does IL-12 do to a T cell?
Promotes T cell replication.
What does Interferon gamma released from T cells do?
Upregulates MHC II expression.
What pathogens do macrophages target?
Intracellular pathogens.
What cells predominantly produces type 1 interferons such as IF-alpha and IF-beta?
Virally infected cells.
What do interferons do?
Promote transcription of anti viral genes. Enhances t cell response by higher MHC expression and tissue repair.
What do anti viral genes promoted by interferons code for?
Nucleases, viral entry/exit inhibitors, viral uncoating inhibitors, protein translation inhibitors.
What interferon is produced for viruses?
Alpha and beta.
What interferon is produced for bacteria?
Gamma.
Virus-infected cells are killed by what immune cells?
Cytotoxic T lymphocytes (CTLs) or Natural Killer (NK) cells.
How does killing of cells prevent spread of pathogens?
Viral replication need cells to replicate. Kills viruses inside. Apoptosis is controlled inflammation.
What can triggers expression of genes that activate cellular effector mechanisms that kill intracellular pathogen?
Binding of complement protein or cytokine to cell surface.
What are the two cellular effector mechanisms that can kill intracellular pathogens?
Reactive Oxygen and Nitric oxide. Acidification and digestion within phagosomes.
What soluble molecules can inhibit microbes?
Complement mediated bacterial destruction. Lectin binding to neutralise cell attachment or entry.
What cell does Th1 primarily activate
Macrophages by interferon gamma.
What cell does Th2 primarily activate?
Eosinophils.
What cell does Th17 primarily activate?
Neutrophils.
What activates innate immune cells?
Detection of microbial ligands (PAMPS). Gene expression changes driven by specific combination of cytokines
What happens to lymphocytes after they recognise antigen and become activated?
Proliferation and differentiation e.g into different t helper cell classes.
What immune cells would you expect to see 3-5 days after infection?
Plasma cells and effector T cells.
T lymphocyte count as we age?
Naive T cell count decreases due to thymic involution but memory T cell count increases.
In a protozoa infection what T cell would be produced?
Th1 cells.
In a fungi infection what T cell would be produced?
Th17 cells.
In a viral infection what T cell would be produced?
Cytotoxic T lymphocytes.
In a helminth infection what T cell would be produced?
Th2 cells.
What immune cell count can be reduced if you get infected by HIV?
Reduced CD4 T helper cells.
In X-linked agammaglobulinaemia what would be reduced in the blood?
Decreased serum IgG of all types.
In Severe combined immunodeficiency (SCID) what would be reduced in the blood?
Low lymphocyte count.
What occurs in chronic granulomatous disease?
Loss of reactive oxygen species production and so neutrophils, monocytes, and macrophages can’t destroy certain microbes.
What occurs in Chédiak-Higashi syndrome?
Compromised lysosomes.
