LOCO Revision2 Flashcards
What are the two types of synoviocytes [2]
Describe their roles [2]
Which one is more prominent? [1]
Type A bone marrow derived macrophage
Type B fibroblast-like connective tissue cell; make hyaluronic acid - more prominent
Synovial fluid anaylsis
What components make SF [3]
Ultrafiltrate of blood
Hyaluronic acid - interacts with proteins like albumin; makes glycoproteic gel
Lubricin
Describe the mucin clot test [1]
Describe how a patient a healthy patients’’s mucin clot test would present [1]
Describe how a patient with RA’s mucin clot test would present [1]
Mucin clot test:
* Sample of SF into vinegar
* Hyaluronic acid will clot
Healthy:
* Big clot
RA:
* Hyaluronate produced is smaller and not polymerised as long (has less molecular weight), so therefore the clot produced in the mucin clot test will be very loose and not sully solidify.
Describe the pathophysiology of RA [4]
RA is primarily a synovial disease and synovitis (inflammation of the synovial lining) occurs when chemoattractants produced in the joint recruit circulating inflammatory cells
- Over-production of TNF-alpha leads to synovitis
and joint destruction
Type A synoviocytes proliferate:
* increase in number of macrophages
* Early RA: Subintima normal
Infiltration of inflammatory cells:
* Synovial fluid: neutrophils
* Subintima: lymphocytes (CD4 T helpers; dendritic cells; macrophages)
* Both become thicker & more dense
Proliferation of fibroblasts in subinitima causing thickening
Generation of new synovial blood vessels is induced by angiogenic cytokines and activated endothelial cells produce adhesion molecules which FORCE LEUCOCYTES into the synovium - where they can trigger inflammation
The synovium proliferates and grows out over the surface of the cartilage (past the joint margins), producing a tumour-like mass called ‘pannus’
- This pannus of inflamed synovium DAMAGES the underlying cartilage by blocking its normal route for nutrition and by direct effects of cytokines on the chondrocytes
The cartilage becomes thin and the underlying bone exposed
- The pannus DESTROYS the articular cartilage and subchondral bone
resulting in bony erosions
RA pathophysiologyy
Which cells infiltrate the synovial fluid? [1]
Which cells infiltrate the synovial subintima? [1]
- Synovial fluid: neutrophils
- Subintima: lymphocytes
State why synovial joints are susceptible to inflammatory injury [2]
Presence of rich network of fenestrated capillaries
* Fenestrated capillaries: become more leaky so plasma and immune cells can enter synovial membrane and joint cavity
Limited ways it can respond
How does the joint respond to RA? [1]
Pro-inflammatory cytokines produced in RA joint push bone marrow cells and macrophages to become osteoclasts
What is a pannus? [1]
Where are pannus created? [1]
What can be the effect of pannus creation ? [2]
Villi like projections caused by proliferation of SF and subintima:
Created at the small microenvironment of bone-cartilage junction
. Concentration of pro-inflammatory cytokines causes increase in osteoclasts and thickening of lining and subintima
Causes synovial membrane to grow over and erode articular cartilage
Synovial fluid of what colour would suggest a bacterial infection
Colourless to pale yellow and clear
Red, brown
Colourless to Yellow and purulent (lumpy)
White/creamy and cloudy/shiny
Yellow and cloudy
Colourless to pale yellow and clear
Red, brown
Colourless to Yellow and purulent (lumpy)
White/creamy and cloudy/shiny
Yellow and cloudy
Perfoming a string test:
How long does normal synoval fluid string before dropping out of pipette? [1]
Normal: 4-6 cm
Which cell types are the first to respond in RA? [1]
Neutrophils
Learn
Describe mechanism of how pannus causes bony erosions [3]
- This pannus of inflamed synovium DAMAGES the underlying cartilage by blocking its normal route for nutrition and by direct effects of cytokines on the chondrocytes
- The cartilage becomes thin and the underlying bone exposed
- The pannus DESTROYS the articular cartilage and subchondral bone
resulting in bony erosions
From PBL answers:
Pannus
Grows over and into the articular cartilage
Produces cytokines that attack cartilage and break it down
Cytokines induce synovial fibroblasts to differentiate into osteoclasts to breakdown peri-articular bone
Which molecules are the most important for causing systemic [1] and within joint [1] effects of rheumatoid arthritis
Systemic: TNF-a
Within the joint: IL-17
Which inflammatory cell types infiltrate blood vessels and form lymphoid nodules in RA? [1]
CD4+ (mainly TH17 subclass) collect around BV: forming small lymphoid vessels
Pannus is destructive: erosion of articular cartilage and bone - destroys the joint
Describe which cells / cytokines are influential in RA synovium [4]
What do each cause to occur / become?
neutrophils
* first responders
* phagocytosing the bacterial infection or some other infection and are citrullinating the proteins in that bacteria so they end up looking like a self-protein that we also citrullinate due to the arginine metabolism pathway
CD4 TH17 cells
* Produce IL-17
* Produce IL-1; IL-6; TNF-a & RANKL
TNF-A
* make synovial fibroblasts - leading to proliferation of synovial membrane
Macrophages:
* Differentiate into osteoclasts
Describe the role Anti-Citrullinated protein antibodies (ACPA) in RA pathogenesis [5]
Anti-Citrullinated protein antibodies (ACPA) can stimulate osteoclast differentiation from monocytes leading to initial bone loss
Osteoclasts then produce IL-8:
* attracts neutrophils
* sensitises nociceptors
* attracts more osteoclasts
Synovitis at start of clinical disease leads to production of cytokines, which stimulate osteoclast proliferation and differentiation
Inducing expression of RANKL, plus synergize with RANKL to enhance bone erosion by more osteoclast differentiation
What is the process of citrullination? [1]
Which process does citrullination occur in? [1]
Which enzyme causes this process to occur? [1]
changing of arginine to citrulline by deamination
This occurs during apoptosis.
done by the enzyme peptidyl arginine deiminase (PADs)
Describe the action of IL-17 in RA [4]
TH17 cells produce lots of IL-17:
* Induces RANKL on synovial fibroblasts
* Stimulates local inflammation
* Active synovial macrophages to secrete pro-inflammatory cytokines: TNF-a; IL-1 & IL-6 - these are the prime drivers of RA
What is the overall net effect of RA on osteoblasts? [1]
Describe the cytokines that drive this effect of osteoblasts to occur [3]
Osteoblasts are switched off:
- (TNF-a, IL-1 & IL-6 produce RANKL to turn on osteoclasts)
- AND
- Induced expression of DKK-1: induces sclerostin (reduces osteoblastic bone formation)
Describe the role of neutrophils in RA [4]
Neutrophils:
- Mount a respiratory burst producing the superoxide anion radical = greater free radical damage
- Breaks down the hyalorunic acid strands - makes it thinner
- Directly induce RANKL
- Produce BAFF (B-cell activating factor) - drives disease process further
- Undergo NETosis
Which of the following depicts RA
A
B
C
D
Which of the following depicts RA
A
B
C
D
What do the arrows point to in this person with RA? [1]
Pannus (or the effects of)
Describe the first [3] and second [3] step that occurs in PAD-dependent differentiation and maturation of osteoclasts
1st step:
* Gradual increase in cell citrullination occurs as a consequence of increased PAD enzyme activity in a calcium-rich microenvironment.
* ACPAs present in the circulation can reach and bind to maturing osteoclasts in the bone marrow, leading to an increase in OC activity and
* consecutive bone resorption through a IL-8 dependent autocrine loop.
Second step:
* IL-8 will reach the joint and initiate the chemoattraction and migration of inflammatory cells, particularly neutrophils.
* Neutrophil extracellular traps are released by neutrophils in the presence of ACPAs,
* This further contributes to the joint inflammation and local accumulation of other inflammatory cells, such as macrophages, and activation of synovial fibroblasts
State and explain the two different subclasses of RA [2]
- Which populations are they more common in? [1]
- Which type of infection are each more common with? [1]
- Which HLA types are more risky for each?
Describe the factors that cause each [4] & [3]
Seropostive (ACPA positive): more common
* Smokers
* Bacterial infections
* HLA DRB1 alleles
* PTPN22
Seronegative (ACPA negative)
* Viral Infections:EBV, cytomegalovirus
* HLA-DR risk alleles
* Contribution of HLA alleles much lower and different (HLA-DR3)
* IRF5 = human interferon regulatory factor-5: Mediates virus induced immune response
Explain the process of NETosis in the initiation of RA [3]
- Ca2+ dependent
- Bacterial stimulus attracts neutrophils
- Neutrophils release NET fibres (made from DNA) that entrap microorganism: forms a scaffold for enzymes, peptides etc. High concentrations kill microbes.
- Results in neutrophils dying / suicidal NETosis
Label A-D of RA symptoms
A: ulnar deviation
B: z-deformity
C: swan neck
D: Boutonniere deformity
RA
Label A & B
A: swan neck deformity
B: Boutonniere deformity
IL-1, Il-6 and and TNF-a leak out into the blood stream in RA and cause systemic inflammation. State 4 diseases this can cause [4]
Anaemia
Thombocytosis
Osteoporosis
Fatigue
Muscle waisting
