RA Symposium Flashcards
What is the goal of RA treatment/
Inflammation naturally fluctuates over time, the goal of treatment is to restore natural natural fluctuations below threshold
Describe the key characteristics of RA
What?Who?Where?,Impact?
- Inflammation of synovial joints, systemic signs
- 3:1 women, aged 40-50, affects 1% of population
- most common, PIP, MCP, wrist
- Increased mortality, reduced quality of life, disability
State three systemic signs of RA along with the cytokine associated
- Low bone density, fractures (TNFa, RANKL)
- Atherosclerosis, MI, stroke (IL6, complement, TNFa)
- Insulin resistance (TNFa, IL1)
- Low stress tolerance, depression (TNFa, IL1, IL6)
- Acute phase response (CRP), iron distribution (hepcidin) (IL6)
(Lipid particles altered, pro inflammatory HDL phenotype, total cholesterol decreased, small HDL increased) - Free fatty acid adipocytokines (TNFa, IL6)
Describe the joint damage in RA
- symmetrical
- morning stiffness
- swelling
- heat
- pain
- loss of function
- redness
- destruction process produces bone erosion and synovial and cartilage damage
What is synovitis?
- swelling over extensor tendons, wrist and MCP joints
- synovium hyperplasia and synovial fibroblasts have reduced apoptosis, enhanced anchorages, unregulated adhesion molecules and increased proliferation
Describe the differences between a normal joint and a rheumatoid joint
Pannus - inflamed synovial membrane Synovial fluid rich in neutrophils Synovitis Cartilage erosion Bone erosion Cartilage loss
What is the composition of synovial tissue in RA?
- ACTIVATED T lymphocytes (40%)
- macrophages (40%)
- B lymphocytes and plasma cells (5%)
- Fibroblasts and endothelial cells (10-15%)
Which immune component is key to RA?
How does this reflect in clinical practice?
- Macrophages
- Key effectors: phagocytosis, APC, cytokine production- TNF, IL1, IL6
- Most therapies decrease macrophage cytokine production
- Decreased macrophage infiltration strongly correlates with the degree of clinical improvement to therapies
Which pro inflammatory cytokines cause disequilibrium of inflammation
IL1
IL6
IL17
What is the role of IL17 in RA
Known to activate synovial fibroblasts and osteoclasts and favour cartilage resorption
Which immune cell is enriched in RA and defected in a way that can be blocked by TNF
Treg
What is the role of B cells in RA
- make autoantibodies present before onset of symptoms
- they form diffuse or follicular infiltrates in the RA synovium
- depletion of B cells using monoclonal anti-CD20 is an effective treatment
Describe the cartilage erosion in RA
- fibroblasts make MMPs which break down the collagen network in the cartilage
- chondrocytes undergo apoptosis
- fibroblasts adhere to and evade the cartilage
- leads to biomechanical dysfunction and joint space narrowing
Which cytokines promote osteoclast differentiation and activation?
- IL17
- RANKL
- TNFa
- IL6
Describe the impact on bone physiology in RA?
- Deep bone resorption pits develop, which become filled with inflammatory tissue
- worse at mechanically vulnerable sites e.g. 2nd/3rd metacarpal
- Little repair as cytokines inhibit differentiation of osteoblasts
Rheumatoid factors is a clinical marker
- What is it?
- Distribution in RA pop
- Clinical relevance
- AB against Fc of another AB –> immune complex formation
- 60-70% patients
- ## Non specific, present in other AID and in healthy people. Some RA patients are seronegative
- Levels do not correlate with disease activity
- RF positive have a more severe disease
CCP anitbody is a clinical marker
- Distribution in RA pop
- Clinical relevance
- 60-70% patients
- High specificity
- Detectable in blood many years before clinical onset
What is citrullination
- Process of replacing protein arginine residues with citrulline residues
- If it occurs on an unusual part of protein it may be recognised as foreign e.g. of citrullinated self protein: a-enolase, keratin, fibrinogen, fibronectin, collagen and vimentin
How might anti-CCP antibodies be considered pathogenic?
- Activation of inflammatory cells by anti-CCP immune complexes
- Anti-CCP mediated neutrophil cell death producing NETs
- Direct binding of anti-CCPs to drive osteoclastogenesis
Consider the aetiology of RA
Polymorphisms are associated with RA. What is the role of HLA DRB1 SE?
Human leukocyte antigen, account for 30-50% of the overall genetic risk
Consider the aetiology of RA
Polymorphisms are associated with RA. What is the role of PTPN22?
Regulates T cell activation
Consider the aetiology of RA
Polymorphisms are associated with RA. What is the role of CTLA4?
Co stimulation suppressor that regulates interactions between T cells and APCs
Consider the aetiology of RA
Polymorphisms are associated with RA. What is the role of STAT4?
Transducer of cytokine signals that regulates proliferation, survival and differentiation of lymphocytes
Consider the aetiology of RA
Polymorphisms are associated with RA. What is the role of TRAF1?
Regulator of TNFa receptor superfamily signalling
Consider the aetiology of RA
What can be said about the genetics of RA?
- Weak genetic component, monozygotic twins 12-15% concordance
- Carrying a risk gene doesn’t mean you will develop disease (epigenetic cause)
- Genes have a low penetrance
Consider the aetiology of RA
How is testosterone involved?
How is pregnancy involved?
- Testosterone is considered to protect against AID….men who get RA usually have low testosterone levels
- Risk of developing RA is increased during the period just after giving birth, breast feeding after the first pregnancy
- RA patients often experience remission during pregnancy (less disease activity and have increased numbers of Treg)
- risk of developing RA after menopause is not influences by hormone replacement therapy
Consider the aetiology of RA
What is the role of smoking
- Heavy smoking of both sexes increases the risk of RA amongst persons with susceptibility HLA DR4 alleles
- HLA DRB1+ most susceptible if smoked and increases risk of being anti CCP+
- TCDD in cigarette smoke has been shown to activate synovial fibroblasts to induces pro inflammatory cytokines
Consider the aetiology of RA
Which infections are associated with RA
Human parvovirus B19 Human retrovirus 5 Alphaviruses Hepatitis Chronic hepatitis C EBV Mycoplasma Ecoli Rubella Porphyromonas gingivitis- found in gums causing periodontitis by causing citrullinisation