Immunology Part 1 (p102-123- immunodeficiencies, hypersensitivity, modulation) Flashcards
What is reticular dysgenesis?
Failure of stem cells to differentiate along myeloid or lymphoid lineage- failed production of neutrophils, lymphocytes, monocytes/macrophages, platelets.
Fatal in early life unless corrected with transplantation
What is Kostmann syndrome?
Specific failure of neutrophil maturation- autosomal recessive severe congenital neutropenia
Classic form due to mutation in HCLS-1 associated protein X-1 (HAX1)
What is cyclic neutropenia?
Specific failure of neutrophil maturation- autosomal dominant episodic neutropenia every 4-6wks
Mutation in neutrophil elastase
What is leukocyte adhesion deficency?
Neutrophils lack adhesion molecules CD11a/CD18 and CD11b/CD18, which normally bind to ligands on endothelial cells and regulate neutrophil adhesion and transmigration so they fail to exit blood stream
What is leukocyte adhesion deficiency characterised by?
High neutrophil count in blood
Absence of pus formation
Delayed umbilical cord separation
What happens in chronic granulomatous disease?
Absent respiratory burst- deficiency of one of the components of NADPH oxidase and subsequent inability to generate oxygen free radicals that kill intracellular microorganisms
Excessive inflammation- persistent neutrophil and macrophage accumulation so inability to degrade antigens
Which bacteria are people with chronic granulomatous disease particularly susceptible to?
Catalase positive- PLACESS: Pseudomonas Listeria Aspergillus Candida E.Coli Staph aureus Serratia
What result would you see for the nitro-blue tetrazolium (NBT) test in a chronic granulomatous patient and why?
Negative- NBT is a dye that changes colour from yellow to blue following interaction with hydrogen peroxide
How does SCID present generally?
Unwell by 3months of age (protected beforehand by IgG from mother across placenta then colostrum) with: Failure to thrive Persistent diarrhoea Skin disease Graft versus host disease
What mutation is involved in X-linked SCID?
45% of SCID
Mutation of gamma chain of IL2 receptor on chromosome Xq13.1 -> inability to respond to cytokines causes early arrest of T cell and NK cell development and immature B cell production
What causes DiGeorge syndrome and what does it feature?
Deletion at 22q11.2 CATCH 22: Cardiac abnormality (ToF) Abnormal facies- high forehead and low ears Thymic aplasia- T cell lymphopenia Cleft palate Hypocalcaemia/hypoparathyroidism 22- chromosome
How are phagocyte deficiencies diagnosed?
NBT or DHR flow cytometry test
NBT changes from yellow to blue following interaction with hydrogen peroxide
DHR is oxidised to rhodamine which is strongly fluorescent following interaction with hydrogen peroxide
How do you treat phagocyte deficiencies?
Aggressive management of infection
Abx prophylaxis
BMT- definitive
What is treatment for chronic granulomatous disease?
IFN-gamma
What different types of complement deficiency are there?
C1q deficiency
Factor B deficiency
C9 deficiency
SLE
What are the consequences of complement deficiencies?
Increased susceptibility to encapsulated bacterial infections
How are complement deficiencies diagnosed?
CH50 and AP50 tests
How do you treat complement deficiencies?
Vaccination, prophylactic Abx, high levels of suspicion + early treatment, screen family members
What do T cell deficiencies increase the likelihood of?
Viral infections (CMV) Fungal infection (pneumocystitis or cryptosporidium Bacterial infections- esp intracellular organisms (TB, salmonella) Early malignancy
What do antibody deficiencies increase the risk of?
Bacterial infections- staph or strep
Toxins (tetanus, diptheria)
Some viral infections (enterovirus)
How are lymphocyte deficiencies diagnosed?
WCC, lymphocyte subsets, serum Ig and electrophoresis, functional tests
How are T cell deficiencies managed?
Infection prophylaxis and treatment, Ig replacement, BMT gene therapy, thymic transplantation in digeorge syndrome
How are B cell deficiencies managed?
Aggressive tx of infection, Ig replacement every 3 weeks, BMT, immunisation in IgA deficiency
What is a type 1 hypersensitivity disorder, what is it mediated by and what are typical symptoms?
Immediate reaction provoked by re-exposure to an allergen. IgE mediated- mast cells release mediators resulting in vasodilators, increased permeability and smooth muscle spasm
Symptoms:
Angioedema, urticaria, rhinoconjunctivitis, wheeze, d+v, ANAPHYLAXISo
How do you treat atopic dermatitis?
Emollients Skin oils Topical steroids Antibiotics PUVA phototherapy
How do you treat a food allergy?
Dietician
Food avoidance
Epipen
How are most allergies diagnosed?
Skin prick test
What is anaphylaxis?
A severe systemic allergic reaction- respiratory difficulty and hypotension
How do you manage anaphylaxis?
Raise legs, 100% oxygen, IM adrenaline 500mcg, inhaled bronchodilators, hydrocortisone 100mg IV, chlorphenamine 10mg IV, IV fluids
What does a negative skin prick test exclude?
IgE mediated allergy
What is a radioallergosorbent test (RAST) used for?
Measure levels of IgE in serum against a particular allergen (peanut)- confirms dx and monitors response to anti-IgE treatment
Indications- when they can’t stop anti-histamines, anaphylaxis hx or severe eczema
What are component-resolved diagnostics?
It measures IgE response to a specific allergen protein e.g. peanuts contain at least 5 major allergens so it can specifically measure one of them
What is the gold standard for assessing food allergy?
Double blind oral food challenge but risk of severe reaction
What is a useful measure of mast cell activation during an acute allergic episode?
Mast cell tryptase
What is a type II hypersensitivity disorder?
IgG or IgM antibody reacts with cell or matrix associated self antigen. Results in tissue damage, receptor blockade/activation
Name as many type II hypersensitivity disorders as possible (13)
Haemolytic disease of Newborn Autoimmune haemolytic anaemia Autoimmune thrombocytopenic purpura Goodpasture's syndrome Pemphigus vulgaris Graves disease Myasthenia Gravis Acute Rheumatic fever Pernicious anaemia Churg-strauss syndrome Wegener's granulomatosis Microscopic polyangiitis Chronic urticaria
What is the pathology of HDN?
Maternal IgG attack antigens on neonatal erythrocytes
How is HDN treated?
Maternal plasma exchange or exchange transfusion
How do you treat autoimmune haemolytic anaemia?
Steroids
What antigen is involved in autoimmune thrombocytopenic purpura?
Glycoprotein IIb/IIIa on platelets
How is autoimmune thrombocytopenic purpura diagnosed?
Anti-platelet antibody
How is autoimmune thrombocytopenic purpura treated?
Steroids, IVIG, Anti-D antibody, splenectomy
What antigen is involved in Goodpasture’s syndrome?
Non collagenous domain of basement membrane collagen type IV
How is Goodpasture’s syndrome diagnosed?
Anti-GBM Ab
Linear smooth IF staining of IgG deposits on BM