Immunology Flashcards
What are some common causes of secondary immunodeficiency?
Age extremes HIV Immunosuppression/Chemo/Radiotherapy/Steroids Malignancy Malnutrition
What kind of infections indicate immune deficiency?
S - serious
P - persistent
U - unusual
R - recurrent
What is reticular dysgenesis?
Failure to differentiate along myeloid lineage - failure to produce neutrophils
What is Kostmann syndrome?
Severe congenital neutropaenia
Autosomal recessive
What brings about leukocyte adhesion deficiency?
Defect in leukocyte integrins (CD18)
What are the clinical features of leukocyte adhesion deficiency?
Leukocytosis
Deep tissue infections
No pus
What causes a chronic granulomatous disease?
Failure of oxidative killing mechanisms
How does a granuloma form?
Organisms are not cleared
Excessive inflammation
Persistent lymphocyte and phagocyte accumulation
Clinical features of chronic granulomatous disease?
Recurrent deep infections (staph, aspergillus, pseudomonas, myco)
Failure to thrive
Lymphadenopathy and hepatosplenomegaly
What does the Nitroblue Tetrazolium test test for?
Chronic granulomatous disease
What organisms hide from immune cells inside normal cells?
Salmonella
Chlamydia
Rickettsia
Where does Mycobacteria hide?
Inside immune cells
What infection prophylaxis is used in phagocyte deficiencies?
Co-trimoxazole
Itraconazole
What is the role of CD4+ cells?
Immunoregulatory
- Activate CD8+ and B cells
- Produce cytokines
HLA Class ii peptide recognition
What is the role of CD8+ cells?
HLA Class i recognition (HLA-A/B/C) Kill cells directly - Produce perforin - Trigger apoptosis - Secrete INFgamma Important in viral/tumour defence
How are B cells activated?
Encounter antigen in lymph node
What is SCID?
Failure of lymphocyte production
Clinical presentation of SCID
Unwell by 3 months Persistent diarrhoea Infections Graft vs Host disease FHx of early infant death
What is the commonest form of SCID and how does it present?
X-linked
Very low/absent T cells
Normal/Raised B cells
Poorly developed lymphoid tissue and thymus
Patient has:
- Low set ears
- High forehead
- Cleft palate
- Small mouth and jaw
- Hypocalcaemia
DiGeorge syndrome
What is type i hypersensitivity?
Immediate hypersensitivity (allergy)
What is type ii hypersensitivity?
Direct cell killing
What is type iii hypersensitivity?
Immune complex mediated
What is type iv hypersensitivity?
Delayed type hypersensitivity
What is an allergy?
An IgE-mediated response to external antigen
What are the clinical features of Type i allergic disease?
Occurs quickly
Influenced by site of contact
What is the pathophysiology of allergic disease?
B cells recognise antigen and produce specific IgE T cells help in IgE production Mast cells - IgE binds to FcEpsilon receptors - Release histamine/tryptase/heparin
What occurs in the inflammatory cascade?
Increased blood flow
Smooth muscle contraction
Increased vascular permeability
Increased mucosal secretions
Is angioedema pitting or non-pitting?
Non-pitting
What happens in Type ii hypersensitivity?
Antibody binds to cell surface Complement activated - Cell lysis - Opsonisation Phagocytosis
What do IgM and IgG act as in Type ii hypersensitivity?
Opsonins
What are some clinical examples of Type ii hypersensitivity?
Transfusion reactions
Goopastures syndrome
Guillan Barre syndrome
How can Type ii hypersensitivity reactions be managed?
Plasmapheresis
Immunosuppression
What happens in type iii hypersensitivity?
Antigen binds to autoantibodies -> Immune complex
Complexes deposit in small vessels
Complement activation
Macrophage and neutrophil infiltration
What are some examples of type iii hypersensitivity/hypersensitivity pneumonitis?
Farmers lung
Bird fanciers lung
Malt workers lung
Etc
What are the symptoms of type iii hypersensitivity reactions and when do they occur?
Dry cough Pyrexia SoB Wheeze 4-8 hours after exposure
Which immune cells mediate Type iv hypersensitivity?
T cells
What happens in type iv hypersensitivity?
Antigen sensitisation T cell priming Subsequent exposure - Activation of primed T cells - Macrophage, neutrophil and lymphocyte recruitment - Inflammation
What are the two types of vaccination?
Active
Passive
What are the two types of active vaccination?
Live attenuated
Inactive
What are the three types of inactive vaccination?
Killed
Subunit
Toxoid
What is passive immunity?
Protection transferred from another person/animal
