Lecture 16- Immune Response to Bacteria/Fungi Flashcards
Pathogen
Bacterium or virus or other microorganism that can cause disease
Opportunistic pathogen
Bacterium, virus or other microorganism that can cause disease in people with impaired immunity but not in healthy individuals
Being a pathogen means to evade ____
Innate immunity
What is an example of a non-pathogen that is resident of mammalian microbiotia
E. Coli K12
What can enteropathogenic and enterotoxigenic eschirichia coli cause
Diarrheal diseases in dogs and cats
What body surface has the most bacterial cells
Colon- 10^12
inflammatory bowl disease is a ____ response to microbiota
Adaptive immune response
How does the immune system respond to non-pathogens
Complement, phagocytosis, adaptive response to microbiota
How do pathogens evade the immune system
Antigenic variation, antigenic drift, molecular mimicry, and virulence factors
What is antigenic variation
Change in H/N molecules
What is an example of antigenic drift with Salmonella
Change in arrangement of promoters leads to differential expression of flagellin protein in salmonella
Facing one way we have repressor citrates so no salmonella, but undergo DNA inversion can turn off repressor and activate salmonella
How does Pili evade immune system
Highly antigenic carries 10-20 silent promoters
What is antigenic drift
Natural mutations over time lead to changes in structure of proteins that may be targeted by antibodies
what is molecular mimicry
Sequence similarities between self and virus
Can result in lack of antibody response to antigen and cross-responsiveness
How is Lyme a example of virulence factor
Resists complement mediated phagocytosis by producing osp proteins that binds Factor H. Acts like C3b binding factor H which causes inactivation of complement
How does a capsule evade the immune system
Inhibits phagocytosis
Important for extracellular bacteria
IgA proteases
Cleave IgA at hinge making ineffective can’t act at mucosal surfaces
Why is sialyation of LPS bad
Salic acid is on host cells not bacteria so LPS is on gram - bacteria can add Salic acid and fake being host cell
What does listeria monocytogenes cause
Gastroenteritis
What does listeria monocytogenes produce
Listeria lysin O or LLO that degrades phagosome and therefore replicates in cytoplasm and hijacks host cell and uses act A to propel itself
What is the innate immune response to intracellular bacteria
Phagocytosis and NK cell activity
Macrophages response to intracellular bacteria
Macrophages secrete IL-12 and IL-15 to recruit NK cells, NK cells will proliferate and secrete INF-y and will bind to macrophages to tell them to increase phagocytosis and release inflammatory cytokines
When will NK cell target foreign invader
Downregulation of MHC I
What is the adaptive response to intracellular bacteria
Cell mediated immunity, IL-12 stimulates TH1 response resulting in INF-y and expression of CD40L to activate macrophages
How do CD8+ T Cells respond to intracellular bacteria
Kill bacteria displaying on MHC I molecules via Perforin and granzymes
How do antibodies respond to intracellular bacteria
They play a minor role but can use ADCC- antibody’s bind target cell, FC receptors on NK cell recognize bound antibodies, crosslinking activates NK cell to release toxic granules and kill cell
How do intracellular bacteria evade immune system
Escape the phagosome, prevent phagosome-lysosome fusion and resistant to lysosomal enzymes
What are the mechanisms of pathogenesis of extracellular bacteria
Release toxins endotoxins and exotoxins
What are endotoxins and example
LPS- activator of macrophages causes release of cytokines and activates alternative complement
What are exotoxins and exmaple
Either stimulate cytokine release or are cytotoxic to other cells
PMT in atrophic rhinitis in swine disrupts cell signaling leads to bone resorption and disrupted bone formation by messing with GPCR’s and disrupting GTP—> GDP and cell will die of apoptosis
What is the innate response to extracellular bacteria
Physical barriers, antimicrobial peptides- lysozymes and defensive
What is the adaptive response to extracellular bacteria
Antibodies
How do fungal pathogens evade immune system
Persistence within phagocytes, inflammation, CTL activity
What type of PRRs do macrophages and dendritic cells express to recognize fungal cell wall components
TLR’s and Dectins
What is the adaptive immune response to fungal pathogens
Cell mediated stimulated by cytokines from dendritic cells
Dendritic cell recognizes a fungal pathogen and results in activation of innate effector cells and _____
Generation of TH1/Th17 adaptive responses
What is the adaptive immune response to intracellular fungi
TH1 and CTL’s
What is the response of the adaptive immune system to extracellular fungi
Th17- stimulate neutrophils
What are some fungal pathogen evasion tactics
Biofilm to resist phagocytosis, mask antigens, capsules, obtain nutrients like iron and zinc, inactive antimicrobial peptides
