Immunology Flashcards
What are SPUR infections? What do they indicate?
Serious, Persistent, Unusual, Recurrent
Indicate immune deficiency
What is the main hallmark of immune deficiency?
Recurrent infections
Primary immune deficiencies are common. True/False?
False
Rare! Secondary immune deficiencies are common
Risk of infection ______ as neutrophil count increases
Decreases
How can failure to produce neutrophils arise?
Failure of stem cell differentiation
Failure of neutrophil maturation
What is Kostmann syndrome?
Rare autosomal recessive disorder; congenital neutropenia
Clinically presents as (recurrent) infections 2 weeks after birth
What is leukocyte adhesion deficiency?
Rare primary immune deficiency where neutrophils fail to bind to endothelial markers - cannot find where infection is!
Genetic defect in CD18
What is chronic granulomatous disease?
Failure of oxidative killing due to inability to generate oxygen free radicals
Name an important related side effect of anti-TNF therapy
Reactivation of latent TB
In congenital neutropenia, neutrophil count is normal. True/False?
False
Low or absent
Is there pus formation in congenital neutropenia?
No
In leukocyte adhesion deficiency, neutrophil count is low during infection. True/False?
False
It is high
Is there pus formation in leukocyte adhesion deficiency?
No
In chronic granulomatous disease, neutrophil count is normal. True/False?
True
Would be raised in the acute stage but not once granuloma has formed
Is there pus formation in chronic granulomatous disease?
Yes
Give examples of definitive management of phagocyte deficiencies
Bone marrow transplant, gene therapy
What cells do T cells arise from?
Haemopoetic stem cells in bone marrow
Defects in stem cell differentiation in haemopoetic cells causes which fatal condition?
Reticular dysgenesis
What is Severe Combined Immunodeficiency (SCID)?
Failure of production of lymphocytes
What are some key clinical phenotypes of SCID?
Unwell by 3 months
Diarrhoea
Failure to thrive
Early death
Why does SCID present only after 3 months of age?
Maternal IgG protects the infant up to this point
In X-linked SCID, which receptor is mutated?
IL2 receptor
What is DiGeorge syndrome?
Failed development of the thymus
“Funny looking kid”
Which chromosome is deleted in DiG syndrome?
22q11
In DiG syndrome, the thymus fails to develop. What is the consequence of this?
Low/no T cells can mature (thus low T cell numbers)
What is hypogammaglobulinaemia?
Failure to produce mature B cells
What is common variable immunodeficiency?
Low IgG, IgA and IgE
Leads to recurrent infections, often autoimmune
Which type of hypersensitivity reaction do allergic diseases come under?
Type 1
Define what is meant by allergy
IgE-mediated response to an external antigen
Describe the hygiene hypothesis
Decrease in infectious exposure in early life predisposes to increased sensitivity/predisposition to allergic stimuli
Allergic reactions typically take a few hours to develop. True/False?
False
Can be from within minutes to a couple hours
What is the role of B lymphocytes in the allergic response?
Recognise antigen and produce IgE
What is the role of T lymphocytes in the allergic response?
Aid B cells in producing IgE
What is the role of mast cells in the allergic response?
Express Fc receptors for IgE
Produce inflammatory mediators upon degranulation
Allergic reactions occur on first exposure to the allergen. True/False?
False
First encounter produces circulatory IgE, which then binds to mast cell; when second encounter occurs, the IgE is activated, causing mast cell degranulation, leading to allergy
What is the clinical effect of histamine and other inflammatory mediators in the lung?
Bronchoconstriction Vasodilation Increased vascular permeability Mucosal oedema, mucus secretion Yellow sputum
What is urticaria? How long does it last?
Hives/rash
Lasts typically 6 hrs
Name some elective investigations for identifying allergic disease
Skin prick test
Challenge testing
What would be measured in an acute anaphylactic episode?
Serum tryptase
What is a skin prick test?
Expose patient to standardised solution of antigen through a prick to the forearm
A positive test will yield a local flare
Which drug class should be discontinued prior to skin prick testing?
Antihistamines for 48hrs
Corticosteroids should be stopped before skin prick testing. True/False?
False
Why is measuring total IgE not useful in diagnosing allergic disease?
IgE can be raised by lots of things - allergy can also occur in the absence of IgE
Which drug supposedly blocks mast cell degranulation?
Sodium chromoglycate
What disease type is an example of Type I hypersensitivity?
Allergy
Type II hypersensitivity involves direct cell killing through which main mechanism/process?
Complement pathway
What are the 4 main effects of Complement activation?
Direct killing (MAC)
Opsonisation (C3b)
Solubilisation of immune complexes
Chemotaxis
Give a clinical example and description of Type II hypersensitivity
Blood transfusions
Can’t give group A patient blood from group B, as they will produce anti-B antibodies and activate Complement, causing massive inflammation
What is plasmapharesis?
Remove pathogenic antibody from a patient’s blood
What mediates Type III hypersensitivity?
Immune complexes
What happens in Type III hypersensitivity?
Immune complexes get stuck in areas and activate Complement in those areas, attracting macrophages and causing phagocytosis
Give a clinical example of Type III hypersensitivity and describe what happens
Farmer’s lung
Inhaled fungal particles stimulate AB production which bind to antigens, triggering Complement and inflammation, resulting in wheeze and malaise
Which cell type mediates Type IV hypersensitivity?
T cells
What happens in Type IV hypersensitivity?
T cells generated due to initial sensitisation of antigen; repeated exposure causes recruitment of inflammatory cells to the site
What term is given to a collection of activated macrophages and lymphocytes?
Granuloma
Give examples of non-autoimmune Type IV hypersensitivity conditions
Sarcoidosis
Tuberculosis
Leprosy
Organ rejection
What are memory B cells?
Generated in primary humoral responses, they survive in a dormant state and rapidly reactivate in response to second encounter with same antigen
What are the 4 main ways of active vaccination?
Exposure to infectious organism
Exposure to similar, less virulent pathogen
Exposure to less virulent form of same organism
Exposure to inactivated organism
What was involved in variolation?
Exposing people to smallpox pustules from infected patients intradermally to provoke immunity
In order to inactivate a pathogen, heat can be used to denature it. What is the problem with this?
Denaturation causes conformational change, so organism isn’t as similar to one we are trying to achieve immunity to
What is the main danger of live attenuated vaccines?
Can cause disease particularly in immunosuppressed individuals
Give examples of live attenuated vaccines
Measles and mumps
Chickenpox
Rubella
Smallpox
Which Ig is contained in colostrum?
IgA
HLA Class II presents to which T cell?
CD4
HLA Class I presents to which T cell?
CD8
Why is HLA matching in transplantation important?
Minimise differences between donor and recipient to prevent transplant rejection
Mathcing HLA Class I is more important than matching HLA Class II. True/False?
False
Class II more important as CD4 cells are the main mediators of the immune response
What are the disadvantages of HLA matching?
Limited benefit if the donor pool is small Rare variants (ethnic groups) may not have good chances
What are the 2 situations where HLA matching is used to allocate donors?
Stem cell transplants
Kidney transplants
When is HLA matching not used to allocate donors?
Lung, heart and liver transplants
What is meant by “cold ischaemic time”?
Amount of time organ is left in ice
Should be as short as possible
Which type of hypersensitivity reaction is acute cellular rejection?
Type IV
What is the time-frame over which acute cellular rejection of a transplant takes place?
5-30 days
Transplantation of donor tissue between blood groups will always result in hyperacute rejection. True/False?
True
Over what time-frame does acute vascular rejection of a transplant occur?
5-30 days
Which type of hypersensitivity reaction is acute vascular rejection of a transplant?
Type II
What is the most major cause of graft loss?
Chronic allograft failure
Over what time-frame does chronic allograft failure occur?
Greater than 30 days