L6 - cytokine regulation of Rheumatoid Arthritis Flashcards
- Describe the clinical features of rheumatoid arthritis (RA) and the key players (e.g., cells, autoantibodies and cytokines) involved in joint inflammation and damage - Discuss risk factors and early immunological events associated with the evolution of RA in patients - Compare how different inflammatory cytokines direct joint inflammation and erosive tissue damage in rheumatoid arthritis - Appraise regulatory cytokines as potential new therapies for the treatment of rheumatoid arthritis - (115 cards)
What is rheumatoid arthritis (RA) and what tissue damage does it cause?
RA is a chronic inflammatory disease affecting joints, causing damage to cartilage and bone. The inflammation-driven erosion of these tissues leads to irreversible joint damage.
What experimental evidence demonstrates cartilage erosion in RA?
In a lab model of inflammatory arthritis, red staining highlights proteoglycans in cartilage. In arthritic joints, reduced red staining shows cartilage erosion due to inflammation
What historical anecdote is associated with early RA treatment in Australia?
In the late 1800s, RA patients were advised to sit inside rotting whale carcasses, supposedly inspired by a man who claimed being cured of rheumatism after drunkenly falling into a whale.
How have RA treatments evolved from historical approaches?
Modern RA treatments involve multimillion-pound blockbuster drugs targeting cytokine-driven mechanisms, providing effective management of the disease.
What are the key clinical features of RA?
Swollen, painful, stiff joints
Symmetrical arthritis (affecting both sides equally)
Leads to irreversible disability due to bone and cartilage damage
How prevalent is RA, and who does it affect most?
RA affects 1% of people worldwide (400,000 in the UK) and is more common in females than males. Onset typically occurs at ages 40-60, slightly later in men.
What is the female to male ratio of rheumatoid arthritis
3:1
What factors may explain why RA affects females more than males?
Possible factors include hormonal influences, particularly the anti-inflammatory effects of oestrogen, though this remains controversial.
Why is early treatment crucial in RA?
Early intervention prevents inflammation and irreversible damage to bone and cartilage, which cannot be reversed once it occurs.
What comorbidities are associated with RA?
Most common: Cardiovascular disease
Others: Mental health issues - fatigue and depression
Severe cases can lead to hand and joint deformations, including joint dislocations
What does an X-ray of a joint affected by RA show compared to a healthy joint?
Healthy joint: Clear joint space and defined bone structure
RA-affected joint: Loss of joint space due to cartilage erosion, painful bone-on-bone movement, and bone erosion
How does RA have both systemic and local characteristics?
Systemic: Autoimmunity (breach of tolerance leading to presence of auto antibodies) and inflammation markers (CRP, ESR)
Local: Immune cell infiltration of the synovium, synovial thickening, and hyperactivated tissue cells
What percentage of RA patients are autoantibody positive, and what autoantibodies are involved?
Around 70% of patients are autoantibody positive. Key autoantibodies include:
Rheumatoid factor (RF): Targets the Fc portion of IgG
Anti-citrullinated protein antibodies (ACPAs): Target post-translationally modified self-proteins
What inflammatory markers are elevated in RA patients?
C-reactive protein (CRP): Acute phase protein indicating systemic inflammation
Erythrocyte sedimentation rate (ESR): Clinical marker for inflammation
What is the role of the synovium in a healthy joint, and how is it affected in RA?
Healthy synovium: Thin lining that produces synovial fluid for joint lubrication
RA synovium: Thickened lining with immune cell infiltration, leading to swelling and tissue damage
How do synovial fibroblasts and osteoclasts contribute to joint damage in RA?
Synovial fibroblasts: Hyperactivated, contributing to inflammation
Osteoclasts: Hyperactivated, leading to bone resorption and erosion
What changes occur in the synovium during RA?
Thickening and swelling of the synovial lining
Immune cell infiltration
Hyperactivation of tissue cells such as fibroblasts and osteoclasts
What role do single nucleotide polymorphisms (SNPs) play in rheumatoid arthritis (RA)?
Over 100 SNIPs have been associated with the development of rheumatoid arthritis, and while a single SNP may only minimally increase the risk, combinations of SNPs can raise the likelihood of developing the disease by up to 40-fold.
How were the single nucleotide polymorphisms (SNPs) associated with rheumatoid arthritis identified
through genome wide association studies (GWAS) and meta analyses
What is the most significant SNP in terms of genetic risk factors for developing rheumatoid arthritis
shared epitope encoded by HLA-DRB1
What is the shared epitope in HLA-DRB1, and why is it significant?
The shared epitope is a five-amino acid sequence in the HLA-DRB1 chain, which is associated with more severe disease, greater damage to cartilage and bone, and higher autoantibody titres. Its discovery led to the shared epitope hypothesis, which suggests that individuals with this epitope are more efficient at presenting autoantigens to T cells.
What non-HLA SNPs are associated with RA, and what processes do they regulate?
Non-HLA SNPs involved in rheumatoid arthritis regulate key processes such as T cell activity, cytokine and chemokine signalling, and immune regulation. FoxO3 is associated with a milder course of RA, while PTPN2 negatively regulates signalling downstream of cytokine and T cell receptors.
What have bioinformaticians looked and compared
GWAS and SNPs to understand their impact on gene expression in patients with RA. The studies found that the genes associated with these SNPs are involved in various processes, including the activation of the immune system, regulation of cytokines and cytokine receptors, and T cell activation.
What is PTPN2
a protein tyrosin phophatase (PTP) that negatively regulates TCR and cytokine signalling (effectively shuts off downstream signalling)