How to fight infection and the body's response Flashcards
Describe the barriers the body has to infection
Antimicrobial factors in salive Mucus and cilia Skin pH Acid Flushing urinary tract
What is phagocytosis?
Cell recognizes and binds to pathogen. This activates the cell to ingest the bacteria (the leading edge and pseudopodium engulf bacterium). Inside the cell, oxidative burst kills it
How does the body respond to bacterial infection?
- Bacteria enter tissue
- Innate cells have PRRs on surface to bind to PAMPS on bacteria
- Bacteria phagocytosed
- At the same time, macrophages release pro-inflammatory cytokines and chemokines
- Cytokines IL-1 and TNF-alpha and chemokine CXCL-8 are released by macrophage
- Mast cells have PRRs on surface and can be activated by proteins
- When activated, mast cells degranulate and release contents into tissue
- Causes blood vessels to swell and become leaky
- Tight junctions between endothelial cells separate - allows contents of blood to get into tissue and immune cells to enter site of infection
- Neutrophils first cell to enter site of infection - engulf and phagocytose bacteria (oxidative bursts and enzymes)
- Complement and c-reactive protein drawn into wound
- Proteins enter area to make bacteria clearer for phagocytes
- Dendrites engulf pathogens and then move to lymph vessel, taking pathogen to lymph node - macrophages can do this too
- In lymph, t-helper cells are waiting to be activated. Dendritic cell enters and breaks down microbe, presenting a portion of in MHC II
- Recognized by T-cell receptor on CD4 helper cell
- In combination with co-signaling process, activates T-helper cell
- Effector T-helper cell replicates and clonally expands
- Activates B-cells to produce antibodies
- IgM enters wound
Which cytokines are released by macrophages?
IL-1 and TNF-alpha
Which chemokine are released by macrophages?
CXCL-8
What happens to mast cells when they are activated?
Degranulate
What do cytokines do?
Communication between cells - can be pro/anti inflammatory
What are interleukins?
Target leukocytes
What are interferons?
Antiviral response
What are chemokine?
Mediate chemotaxis
What are the three mechanisms that can activate complement proteins?
Alternative, classical and Mannose-binding lectin pathway
What is the alternative pathway to activate complement proteins?
Complement protein binds to microbe itself
What is the classical pathway to activate complement proteins?
Antibodies bind to bacteria which activates the pathway
What is the MBL pathway to activate complement proteins?
MBL binds to microbe initially to initiate pathway
What is the common result of activating complement proteins?
C3a is produced to instigate the inflammatory process
What does C3b do?
Opsonize and phagocytose microbes
Where are acute phase proteins produced?
Liver
Which chemicals signals the liver to produce acute phase proteins?
IL-6
What doe acute phase proteins do?
Opsonize
Activate complement cascade
What do TH2 cells do?
Activate B-cells to produce plasma cells to produce antibodies
How are B-cells activated?
- Activated when antigen presented to T-helper cell
- When T-cell activated, B-cell is activated too
- Co-stimulatory signals and cytokines enables B-cells to become active
- B-cells clonally expand
- B-cells can differentiate into plasma cells or memory cells which reside in lymph
What is isotope switching?
Producing different types of anitbody
What is the first antibody to be produced?
IgM
What is opsonisation?
Highlights pathogen to phagocyte
Helps phagocytosis
Important for encapsulated bacteria and viruses
How does inflammation occur?
Antibodies stimulate mast cells to degranulate
What is cytotoxicity?
Cytotoxic T-cells and Nk cells bind to antibody
Release enzymes for cytotoxic cell, leads to apoptosis
How does the body respond to viral infection?
- Invades epithelial cells
- Spreads to neighboring cells
- Cells produce IFN-alpha
- Stops replication of viruses within tissue
- Infected cell presents particles on MHC I receptor
- Mast cells degranulate - break in tight junctions and leaky vessels
- Neutrophils degranulate
- Proteins enter area to regulate inflammatory response
- Pathogenic antigens taken up by dendritic cells - T and B cells are activated
- Antibodies bind to pathogens
- NK cells cause apoptosis
What are TH1 cells?
Part of cell-mediated response
NK cells and cytotoxic T-cells
What doe TH1 cells produce
B-cells
How are CD8 cells activated?
MHC I presents antigen to CD8
TH1 activates, which produces IL-2 and IFN-gamma
Helps activate CD8
What does CD8 cell do?
Travels to site of infection by recognising MHC 1 antigen on pathogen
Can use death signal/releae enzymes
How are NK cells activated?
TH1 cell produces IFN-gamma and Il-2
How are macrophages activated?
TH1 cell produces IFN-gamma
How is a plasma cell made?
TH1 cell produces IFN-gamma which stimulates a B cell to turn into a plasma cell
What doe NK cells do?
Activate macrophages
Increase cytotoxicity
Function of neutrophil
Chemotaxis and phagocytosis
Function of monocyte
Phagocytosis
Function of NK cell
Opsonization
Function of T-cell
Mitogen response
Function of T-helper cell
B-cell activation
Function of cytotoxic T-cell?
Nk cell activation
Why do wounds get hot?
Capillary widening
Increased blood flow
Why do wounds get red?
Increased permeability
Fluid released into tissues
Why are wounds tender?
Leukocytes attracted
Extravasation of leukocytes to site of injury
Characteristics of acute inflammation
Duration less than 3 weeks
Not necessarily associated with tissue destruction
Lots of neutrophils
Inflamed
Characteristics of chronic inflammation
Lasts longer than 6 weeks
Significant tissue destruction
Macrophages, lymphocytes and their derivatives are characteristically dominant
