HS III Flashcards
What type of reaction is a type III hypersensitivity reaction?
Immune complex deposition, targeting soluble antigens
How long does a type III hypersensitivity reaction take to develop?
3-8 hours
Which immunoglobulin is involved in type III hypersensitivity reactions and how does it cause a reaction?
IgG/IgM antibodies
React with soluble antigens to form immune complexes that are deposited in tissue and release toxins that damage the tissue
What factors affect immune complex pathogenesis?
Size of immune complex (big/small easily cleared)
Haemodynamic factors, clearance
Host response, low affinity antibodies less likely to form immune complexes
Complement deficiency, clearance
Describe the immune mechanism of type III hypersensitivity reactions
IgG/IgM antibodies bind with soluble antigens to form medium sized immune complexes that are deposited in tissue
Complement is activated
Neutrophil chemotaxis
Neutrophil binds to tissue and releases toxins
What antibodies are tested for in rheumatoid arthritis?
Autoantibody to rheumatoid factor (IgG)
Anti-cyclic citrullinated peptide (Anti-CCP)
Anti-citrullinated protein antibody (ACPA)
Describe the pathophysiology of rheumatoid arthritis
Chemoattractants in joints recruit B and T lymphocytes
Lymphocytes interact and drive overproduction of tumour necrosis factor, which causes synovitis and joint destruction
TNF also stimulates overproduction of IL 6 and other cytokines, recruiting more inflammatory cells
Describe how the lungs can be affected by rheumatoid arthritis
Nodules
Pleural effusion
Interstitial lung disease
Name non-articular manifestations of rheumatoid arthritis
Pericarditis Nodules Pleural effusion Interstitial lung disease Ankle oedema
Describe the articular manifestations of rheumatoid arthritis
Progressive, symmetrical, peripheral, polyarthritis with persistent synovitis and systemic inflammation
Describe the typical presentation of rheumatoid arthritis
30-50 years old
More likely female
Smoking risk factor
Chronic, symmetrical joint pain in the small joints
Morning stiffness lasting longer than 30 mins
Inflammed joints, hot and tender
Rheumatoid nodules
Which specific joints are typically affected?
Proximal interphalangeal joints and metacarpophalangeal
How is rheumatoid arthritis treated?
Corticosteroid: Prednisolone
+DMARD: Methotrexate/hydroxychloroquine
Describe the pathophysiology of glomerulonephritis
Infection with Hep B or bacterial endocarditis, IgG immune complex deposition in GBM, kidney damage
Describe typical X ray findings for rheumatoid arthritis
Narrowing of joint space
Osteoperosis localised to metacarpopharangeal joints
Small erosions at proximal phalanges
Soft tissue swelling involving all fingers
Name a monoclonal antibody used to treat rheumatoid arthritis
Tumour necrosis factor antibody
Describe how monoclonal antibodies can work in autoimmune disease
Bind to cell surface receptor to activate or inhibit signalling within cell
Bind to and be internalised by cancer cells to deliver toxins
Block inhibitory effects on T cells
Describe how monoclonal antibodies can be used to treat breast cancer
Trastuzumab
Inhibits HER-2 signalling (oncogene)
Describe how monoclonal antibodies can be used to treat lymphoma
Rituximab
CD 20 is expressed on all B cell surfaces, and rituximab is an antibody against CD20
Describe the pathophysiology of systemic lupus erythematosus
Self antigens form and the immune system fails to inactivate the B and T lymphocytes that recognise the self antigens - breakdown of tolerance
Autoantibodies form immune complexes that are deposited in tissues
Complement is activated
Influx of neutrophils, causing inflammation
Abnormal cytokine production
What features indicate systemic lupus erythematosus?
Antinuclear antibody present Renal abnormalities Arthritis Photosensitive Oral ulcers Malar rash Arthralga
How is systemic lupus erythematosus treated?
Corticosteriods: Prednisolone
DMARDs: Hydroxychloroquine/Azathioprine
Lifestyle modification and use of suncream
What antibodies are tested for in systemic lupus erythematosus?
Antinuclear antibodies (dsDNA)
Anti-Sm antibodies
Antiphospholipid antibodies
Describe the features of skin involvement in systemic lupus erythematosus
Butterfly/malar rash on face Photosensitivity Urticaria Vasculitis Purpura
