Key Concepts for Test 1 Flashcards
Cells respond to insult via…
Degeneration and atrophy
Apoptosis and necrosis
Inflammation
Regeneration, hyperplasia, hypertrophy
Dysplasia and neoplasia
Structural changes - gross changes, microscopic
What are the 3 steps in PCR
Denaturation, Anealing primers, DNA synthesis
What is the most important factor in the denaturation phase?
The temperature to which the solution is raised too must be determined by the enzyme used. 94-98C
What is the factor that needs to be regulated closely in the annealing phase?
The lowering of the temperature otherwise, the primers may join to sections of the DNA other than the target sequence resulting in the replication of unwanted material. 55-70C
What factor must be tightly controlled in the DNA synthesis phase of PCR?
The time allowed for elongation as this will control the length of the DNA fragment produced. 65-72C
What are the inheritance features of an autosomal recessive disease?
The carriers are asymptomatic, typically not seen in parents, males and females equally affected
Risk 1:4
What are the inheritance features of an Autosomal Dominant Disease?
Phenotype typically appears in every generation, Risk 1:2 at least one parent will display the phenotype
What are the inheritance features of a recessive x-linked disease?
Sons only inherit this from the mother, A male will pass on condition to all daughters, the incidence of disease is much higher in males
Disease is milder in women due to random X inactivation
What are the inheritance features of a dominant x-linked disease
Male parents have no affected sons but all daughters affected
Females typically have a less severe disease
More common for females to have the disease
What are the inheritance features of a Y linked dominant disease?
Disease can only pass from male to male
Only males are affected
All sons of affected male are affected
What occurs in oncotic cell death?
The cell loses control of the composition of its ions due to trauma resulting in swelling causing lysis and cell death resulting in inflammation
What occurs in Necroptosis?
Death ligands (TNF and FasL) activate receptors which turn on protein kinases RIPK 1-3 causing mitochondrial dysfunction leading to a build up in reactive oxygen species resulting in lipase activation and messy cell death
What occurs in pyroptosis?
Bacterial products activate the inflammasome, which activates the caspase-1 protease resulting in cell lysis and inflammation
pro-IL-1B is cleaved to IL-1B a proinflammatory cytokine.
What is the purpose of pyroptosis?
To prevent against the intracellular replication of bacteria and to alert the immune system to the presence of invaders
What occurs in apoptosis?
This is a more natural and clean way of removing cells that are old and need to be turned over, or if they are in excess to requirements. This is a process which retains an intact cell membrane stopping inflammation provided the budding off apoptotic bodies are phagocytosed before they degrade
What occurs in Autophagic cell death?
Double membrane vacuoles enclose cytoplasm or organelles to form autophagosomes, these then fuse with a lysosome to form an autolysosome
What triggers Ferroptosis
Triggered by oxidative stress (ROS) when iron is abundant. Generates lipid peroxides which damage the lipids in membranes
What is Coagulative Necrosis?
Dead tissue is firm, retain its initial shape until removed by inflammatory cells and replaced with scar tissues. This can result in lesions that persist for years due to inaccessibility
What is Colliquative necrosis?
Occurs when a cerebral blood vessel has been blocked, which results in digestion of brain tissue and cyst being formed by glial cells
What is Gas Gangrene?
Deep wounds stop blood flow resulting in bacterial growth which releases and alpha toxin destroying an rotting cells while affected tissues turn black as haemoglobin is destroyed to provide iron for bacterial growth
What is Dry Gangrene?
Arteries are slowly narrowed by atherosclerosis leading to tissue death through desiccation and black colour formation due to blood breakdown
What is suppurative necrosis?
Bacterial infections cause necrosis resulting in neutrophils liquefying tissues to from an abscess
What is Caseous necrosis?
As seen in tuberculosis, when chronic inflammation has resulted in dead cells forming a cheese like debris rich in lipids and proteins
What are the three ‘go’ signals for inflammation?
Neuronic release of bioactive peptides
Intracellular molecules are released from broken cells
Microbial products or toxins are recognised
What are the four cascades of inflammation?
Coagulation, fibrinolytic, kinin, complement
What is the affect of the coagulation cascade?
Activation of thrombin resulting in fibrinogen conversion to fibrin causing clots
Protein activated receptors induce vascular permeability and platelet activating factor release causing its affects
What is the affect of the fibrinolytic cascade?
Generation of the protease plasmin degrades fibrin breaking down clots
Cleavage of Extracellular matrix and activation of matrix metalloproteases causing remodeling of the tissue
Activation of the kallikrein protein which activates the kinin system
What is the affect of the kinin cascade?
Kallikrein release the bradykinin protein resulting in vascular dilatation, vascular permeability and pain inducing affects
What are the cleavage products in the complement cascade system?
C3a, C3B, C5a and components of the membrane attack complex
What are the 5 steps of Mobilisation
- Attraction to sites of injury or infection
- Margination
- Adhesion
- Transmigration
- Chemotaxis
What occurs in the first step of mobilisation (attraction)
DAMPs bind to receptors on macrophages and trigger intracellular signalling cascades. Cytokines IL-1a and B signal to endothelial cells activating them
What is margination
When activated endothelial cells become adhesive for neutrophils by expressing P and E selectins causing them to stick and roll through interaction with sialyl-Lewis-X.
What is the role of P and E selectins?
To allow for neutrophils to loosely contact the vessel wall rolling along its surface
What causes adhesion flattening of neutrophils?
Upregulation of Intracellular adhesion molecule-1 and vascular adhesion molecule 1 as well as leukocyte function associated antigen 1 on neutrophils
What is transmigration?
Movement of neutrophils through the endothelial cells with use of enzymes to remove the basement membrane
What is chemotaxis
Neutrophils move towards site of infection. Chemotactic signals are released to recruit more immune cells
What are the steps of function (phagocytosis, degranulation)
- Opsonisation
- Adhesion
- Phagocytosis
- Degranulation
- Respiratory Burst
What occurs in opsonization, adhesion and phagocytosis ?
Opsonization tags damaged cells and C3B recognition. Phagocytes bind to opsonins.
Becomes phagosomes
What happens in degranulation
Phagosomes fuse with lysosomes creating phagolysosomes and removes visible lysosomes from cytoplasm
What is the process involved in producing a respiratory burst?
NADPH oxidase assembles and reduces oxygen to superoxide, this results in rapid entry of K+ counter ion, The super oxides is reduced to hydrogen peroxide by super oxide dismutase, which then reacts with Myeloperoxidase to form hypochlorous acid which kills the pathogen
What are the four phases of repair?
Haemostasis, Inflammation, Proliferation, Remodelling
What occurs in haemostasis?
Platelets aggregate and degranulate at sites of blood vessel damage, conversion of fibrinogen to fibrin with cross link between fibrin being made by fibronectin and other transglutaminases
What occurs in the inflammatory response?
Removal of necrotic tissue through the actions of both neutrophils and macrophages
These secrete proteases which liquify the necrotic tissue, generate antimicrobial products such as free radicals
What occurs in the proliferation response?
Stromal and epithelial tissue regrows
Fibroblasts proliferate and form a new matrix out of collagen, fibronectin and glycosaminoglycans
What occurs to fibroblasts in the proliferation phase of repair?
They differentiate into myofibroblasts when stimulated by Platlet-derived-growth factor and transforming growth factor which interact with ED-A Fibronectin which results in provision of mechanical tension
What is the role of endothelial cells in the proliferation phase?
New capillaries (angiogenesis) are formed in response to VEGF, pericytes stabilize these in response to PDGF
Endothelial progenitor stem cells from bone marrow can be used to generate new BV (vasculogenesis)
What occurs in the remodelling phase of repair?
Granulation tissue is exchanged for scar tissue which lacks cells, collagen III is replaced by parallel collagen, and equilibrium is reached between collagen deposition and MMP degradation, strength of collagen fibres results in crosslinks
Acute Inflammation: Innate Immune system
(cell action)
- Circulating neutrophils
- Monocytes -> macrophages
Recruited to site of damage Phagocytose debris, DAMPs, microbes
Kill microbes
Regulate inflam and repair
Pro-Inflammatory cytokines and chemokines (IL-6, TNF, IL-1B) attract immune cells
Proteases digest ECM
ROS
Chronic Inflammation: Adaptive Immune System
(cell action)
- Macrophages acts as Antigen Presenting Cells
- Phagocytosis of microbes and macromolecules
-Process into antigens
-Present to lymphocytes to regulate their activities - Lymphocytes recognize antigen epitopes as foreign by surface receptors.
T Cells: include killer (CD8) and helper (CD4)
B Cells: differentiate into plasma cells to produce antibodies
TB immediate host control
MTB droplets -> alveoli -> alveolar macrophages phagocytose and bacteria replicate in macrophage endosome. Release of TNF and IL-1 recruit neutrophils. Intracellular bacteria destroyed by autophagy, ROS and anti-microbial peptides. Apoptotic cell death induced by PAMPS releases MTB. Phagocytosis of apoptotic bodies and macrophages switch to anti-inflammatory.
TB adaptive immunity and control
Phagocytes migrate to lymph nodes as antigen presenting cells to activate TH1 cells. TAKES WEEKS
Release IFNy to activate apoptosis of infected cells. TH17 cells release IL-17 recruiting neutrophils to cause tissue necrosis
Escape of MTB and dormancy
MTB lipids inhibit M0 activation and generate permissive macrophages that allow intracellular proliferation
Associate into granulomas to impede T cell penetration and antigen presentation
Neutrophil toxins favour macrophage necroptosis freeing intact Mtb which is phagocytosed but no lysis in cell.
Treg suppresses TH1 activity
TH2 release IL-4 to generate fibrosis (scar) to block access of TH1 cells.
Granuloma, caseous necrosis leads to dormancy
What is debridement?
Necrotic tissue removal
Neutrophils and macrophages phagocytose tissue debris. Collagenases liquify tissue. Generate ROS and secrete growth factors for fibroblasts. Process antigens to present to T cells to active adaptive immunity
