Immunology of infectious disease Flashcards
What are the bacteria that multiply outside of the host cell?
- Staph
- Strep
- E.coli
- Clostridium
What are the two means that extracellular bacteria cause cell damage?
- Induction of inflammation
- Toxins that kill the host cells
How does the cell combat extracellular bacterial?
Kill them or neutralize the toxins
What are the cells that can do phagocytosis? Where are each generally found?
PMNs–bloodstream
Macrophages–tissues
How does phagocytosis identify bacteria?
Recognize bacterial structures (e.g. polysaccharides, peptides)
What is the first cell that arrives to the site of inflammation?
PMNs
What is the receptor for LPS?
TLR4
What is the peptide sequence that phagocytes recognize on bacteria?
RGD (arg, Gly, Aspartate)
What are the main immunological responders to tissue borne antigens?
Lymphocytes
Where in the lymphatic system do phagocytic cells reside?
Lymph nodes
Spleen
Bacterial DNA contains what motif that can activate macrophages?
Unmethylated CpG dinucleotide
What are the receptors on phagocytic cells that can respond to bacteria?
Fc receptors Complement receptors Scavenger receptors Lectins TLRs
What type of bacteria is complement especially important for?
Those with polysaccharide capsule
What cells release lactoferrin? What is the MOA of this?
PMNs
Lower local Fe concentrations to combat bacteria
What is the role of histamine in immunity?
Enhances inflammatory process by upregulating proteins on endothelial cells to aid in extravasation
What is the classical pathway?
IgG or IgM binds to bacteria, causing C1 to bind to Fc region, and activating the Attack complex
What is the alternative pathway of complement pathway?
Spontaneously hydrolysis of C3b will attach to bacteria to form the attack complex (C5-9)
Deficiencies in C5-C9 predisposed to what infections? Why?
Neisseria meningitidis infections
Neisseria for some reason needs all complements
What is the role of C5-C9 (in terms of gram positive and negatives)?
Lyses gram negative bacteria (can pop holes since lacks peptidoglycan layer)
Opsonizes gram positive
What is the main adaptive immune response to extracellular bacteria?
Humoral response (IgG)
What is the role of antibodies in extracellular bacterial infection ?
- Enhances opsonization
- Neutralize toxins
- Activate complement
What are the two types of antibodies that activate complement?
IgG and IgM
What is the only class of Ab that can cross the placenta?
IgG
How long does it take for maternal IgG levels to disappear in the neonate? What three specific infections are the
3-6 months
- Strep pneumoniae
- Neisseria meningitidis
- HiB
What is the longest lived ab? How long does this last?
IgG
3 weeks
What is the protein on S. Pyogenes and S. Pneumoniae that is a target for ab? What is the function of this?
M protein
Antigenic variation b/t species
Does IgA fix complement?
Yes
What antibody can take the place of IgA in selective IgA deficiency?
IgM
What cytokine is the most potent activator of macrophages?
IFN-gamma
What are IgA antibodies secreted with?
J chain
What is the role of the polysaccharide capsules on bacteria?
Resist phagocytosis, and may inhibit complement activation
What are the bacteria that can vary their surface antigen?
- Neisseria
- E.coli
- HiB