Immune Disorders Flashcards
Reactive arthritis
Infection with certain bacteria presents antigens that cross-react with antigens in the joints
Sympathetic ophthalmia
Damage to the good eye after trauma or surgery to the other – these antibodies are normally hidden or sequestered from the immune system. A type of frank autoimmune disease.
Autoimmune orchitis
Damage to the testicles following mumps or testicular trauma due to release of sperm antigens. A type of frank autoimmune disease.
Rheumatic fever
Due to cross-reaction between streptococcal pyogenes antigens and antigens in cardiac muscle (and elsewhere)
Thyrotoxicosis
Caused by antibodies against the TSH receptor which mimic the action of TSH and stimulate the thyroid gland (Graves)
Pernicious anaemia
Due to malabsorption of vitamin B12 due to autoimmune destruction of the parietal cells in the stomach which produce intrinsic factor or antibodies against intrinsic factor itself
Idiopathic thrombocytopenic pupura
Due to antibodies against platelets
Addison’s disease
Due to destruction of the adrenal cortex
Myasthenia gravis
Due to autoantibodies blocking the acetylcholine receptor on the neuromuscular endplate
Rheumatoid arthritis
Type III hypersensitivity reaction
Soluble antigen and antibody complex precipitates and deposits in vessels and joints
Goodpasture’s syndrome
Antibodies against type IV collagen in glomerular basement membrane, eventually leading to bleeding from the lungs and kidney failure
Hashimoto’s disease
Antibodies against thyroid tissue itself, causing destruction of the thyroid rather than upregulation of the function as seen in Graves
SLE treatment
Immunosuppressive drugs e.g., corticosteroids, azathioprine, cyclophosphamide
SLE
Associated with deficiencies of complement components, thought to be due to impaired clearance of immune complexes. Systemic –symptoms include fever, rash, joint pain and fatigue.
Urticaria
Itchy, raised, transient weals
Can be acute or chronic, often seen in anaphylaxis
Bullous pemphigoid
Autoimmune reaction against two proteins in the hemidesmosomes which help stick the epidermis to the dermis
Can be neural, skin or muscular and these can cross-react to cause symptoms in more than one area
Pemphigus vulgaris
Autoimmune reaction against desmogleins in the desmosomes that help keratinocytes stick to each other
Produces shallow blisters and skin erosions
Pemphigus vulgaris treatment
Rituximab: depletes B cells
Example of viral live attenuated vaccine
MMR, oral polio and chickenpox
Example of bacterial live attenuated vaccine
TB and typhoid
Example of reassorted live attenuated vaccine
Rotavirus
4 types of inactivated vaccine
Whole/fractioned
Protein-based
Polysaccharide-based
Conjugate polysaccharide
Examples of whole viral vaccine
Influenza, injected polio, rabies, Hep A
Examples of whole bacterial vaccine
Pertussis, typhoid, cholera
Examples of fractional vaccines
Subunits: Hep B, influenza
Toxoids: diptheria, tetanis
Negatives of inactivated vaccines
Can’t get lifelong immunity just from one dose, repeat immunisation necessary
How is the Hep B vaccine made?
Hep B is a recombinant vaccine where a segment of the Hep B virus gene is implanted into the yeast expression system
LAIV
Live attenuated influenza vaccine
Recombinant vaccine engineered to replicate effectively the mucosa of the nasopharynx but not the lungs
Tetanus
Caused by clostridium tetani, an anaerobic, spore-forming, gram-positive bacillus that is penicillin-sensitive
Spores are wide-spread, particularly in manure and soil
Easily introduced at time of injury, especially deep, penetrating, dirty wounds
Bacteria produces toxin called tetanospasmin toxin. Causes severe, painful muscle rigidity. Symptoms start about 10 days after exposure
Neonatal tetanus
Entry via umbilicus to infant from unimmunised mother
Infant has no passive IgG immunity
Generally failure of aseptic technique during birth in developing world
Passive immunisation for tetanus
Human or equine tetanus immunoglobulin – acquire immunity by transfer of serum from a donor to a non-immune person
Neutralises unbound toxin and shortens the course, lessens the severity of the disease and improves survival
Passive immunisation advantages and disadvantages
Advantages: immediate protection
Disadvantages: no long-term protection, risk of transmission of other disease from donor, expensive, serum sickness risk
Bordatella pertussis
Whooping cough
Deposited in respiratory tract by aerosol droplets produced by cough
3 stages: catarrhal phase (runny nose, conjunctivitis), paroxysmal phase (whooping), then convalescent phase (recovery, lasts weeks to months)
Whooping cough treatment
Erythromycin – does little when illness already established, may shorten illness if started early but main advantage is decreased infectivity
Whooping cough complications
Secondary bacterial infections such as pneumonia
Encephalopathy, seizures, apnoea
Pertussis vaccine
1) Whole cell vaccine (old) – local and systemic reactions possible
2) Acellular vaccine – 3 dose primary schedule with 2 booster doses
Poliomyelitis
Destroys lower motor neurons resulting in paralysis due to poliovirus
Polio vaccine
Oral version is live and used in epidemics, however, inactivated polio vaccine is incredible effective and has lower risk of vaccine-associated paralytic polio disease
Classifications of immunodeficiency
Congenital vs acquired
Primary vs secondary
When should you suspect immunodeficiency?
When a patient has recurrent bacterial infections or infections with unusual organisms
When should you suspect secondary immunodeficiency?
In patients taking steroid or cytotoxic drugs
In patients with known disease in other organ systems
In patients with lifestyle risk factors for HIV
Antigen and antibody effects on immune responsiveness
The nature of the antigen affects the sorts of responses that are generated
How an antigen is processed and the nature of the MHC presentation structures affect which epitopes are available for recognition by T and B lymphocytes
Antibodies present in an individual at the time of antigen exposure can either enhance immune responses against the antigen by opsonisation or diminish responses by leading to rapid antigen removal
Link between the nervous system and the immune system
Brain controls autonomic nervous system and the endocrine system. The endocrine system releases hormones, which is also regulated by the autonomic nervous system by feeding information through nerves. Nerves and hormones both affect the immune system, which releases cytokines, which affect the brain and the endocrine system.
Effect of corticosteroids on the immune system
Corticosteroids produced by the adrenal cortex have profound immunosuppressive effects by depressing in vivo responses, depressing phagocytosis, inhibiting macrophage activation, inhibiting B and T cell activation and decreasing the number of cells in the thymus.
