Immunology Flashcards
What are SPUR infections?
Serious infections
Persistent infections
Unusual infections
Recurrent infections
What would make you think a patient had a serious infection?
If they were unresponsive to oral antibiotics
What two things would make you suspect persistent infections in a patient?
- Early structural damage
2. Chronic infections
What two things would make you think a patient had an unusual infection?
- Unusualy organisms
2. Unusual sites
What would you class as recurrent infections?
Two major or one major and recurrent minor infections in one year
Give 6 features that may be suggestive of primary immune deficiency
- Weight loss or failure to thrive
- Severe skin rash (eczema)
- Chronic diarrhoea
- Mouth ulceration
- Unusual autoimmune disease
- Family history
What can immunedeficiencies be classed into?
Secondary and primary
What type of immunodeficiencies are common, often subtle and often involve more than one component of the immune system?
Secondary
What type of immunodeficiencies are rare (1:10,000 live births)?
Primary
Give 5 conditions associated with secondary immune deficiency
- Physiological immune deificency
- Infection
- Treatment interventions
- Malignancy
- Biochemical and nutritional disorders
What two things can lead to physiological immune deficiency?
Ageing and prematurity
What are HIV (human immunodeficiency virus) and measles associated with?
Secondary immune deficiency (infection)
What three treatment interventions can lead to secondary immune deficiency?
- Immunosuppressive therapy
- Anti-cancer agents
- Corticosteroids
What 2 malignancies are associated with secondary immune deficiency?
Cancer of immune system - lymphoma, leukaemia, myeloma
Metastatic tumours
Give 4 biochemical and nutritional disorders associated with secondary immune deficiency
- Malnutrition
- Renal insufficiency/dialysis
- Type I and type II diabetes
- Specific mineral deficiencies e.g. iron and zinc
Name 4 innate immune system cells
- Macrophages
- Neutrophils
- Mast cells
- Natural killer cells
Name 3 innate immune system proteins
- Complement
- Acute phase proteins
- Cytokines
Name two cells and one protein of the acquired immune system
T lymphocytes and B lymphocytes
Antibody
What are macrophages and neutrophils?
Phagocytes
What cells: initiate and amplify the inflammatory response, sscavenge cellular and infectious debris, ingest and kill microorganisms, produce inflammatory molecules which regulate other components of the immuen system and resolution and repair?
Phagocytes - macrophages/monocytes and neutrophils
What is the main clinical feature of phagocyte deficiencies?
Recurrent infections
Name three bacteria which can give recurrent infections in phagocyte deficient patients
- Staphylococcus aureus
- Burkholderia cepacia
- Mycobacteria both TB and atypical
Name two fungi which can cause recurrent infections in phagocyte deficient patients
Candida
Aspergillus
What disease is treated by chemotherapy or radiotherapy that kills bone-marrow derived cells, including neutrophils?
Leukaemia
Where are neutrophil precursors initially located?
In the bone
What three problems can cause phagocyte deficiency?
- Defects of phagocyte production
- Defects of phagocyte mobilisation
- Defects of phagocyte recruitment
What does failure of stem cells to differentiate along myeloid lineage lead to?
Failure to produce neutrophils
Name a primary and secondary defect for failure of stem cells to differentiate along myeloid lineage
Primary defect: recticular dysgenesis
Secondary defect: after stem cell transplantation
What can specific failure of neutrophil maturation lead to?
Failure to produce neutrophils
Give two diseases associated with specific failure of neutrophil maturation
Kostmann syndrome: severe congenital neutropaenia
Cyclic neutropaenia: episodic neutropaenia every 4-6 weeks
What two features can ultimately lead to failure to produce neutrophils?
- Failure of stem cells to differentiate along myeloid lineage
- Specific failure of neutrophil maturation
At what point in the leukocyte lineage does recticular dysgenesis occur?
Before hematopoietic stem cell differentiation into common myeloid progenitor and common lymphoid progenitor
At what point of the leukocyte lineage does Kostmann syndrome occur?
Between the differentiation of granulocyte-monocyte progenitor into neutrophil
What is Kostmann syndrome?
A rare autosomal recessive disorder, severe chronic neutropenia
What is the normal neutrophil count, and what is the neutrophil count in a patient with Kostmann syndrome?
Normal > 3000/uL
Kostmann syndrome < 200/uL
How do babies with Kostmann syndrome clinically present?
Infections, usually within 2 weeks after birth:
Recurrent bacterial infection and systemic or localised infection
Name 4 non specific features of Kostmann syndrome
- Fever
- Irritability
- Oral ulceration
- Failure to thrive
What are 2 supportive treatments for Kostmann syndrome?
Prophylactic antibiotics
Prophylactic antifungals
Give two definitive treatments for Kostmann syndrome
- Stem cell transplantation - defect is in the neutrophil precursor, so strategy is to replace all precursors with allogeneic stem cells and start again
- Granulocyte colony stimulating factor (G-CSF) - give specific growth factor to assist maturation of neutrophils
What would you expect to happen if a patients phagocytes were unable to recognise endothelial adhesion molecules?
Leukocyte adhesion deficiency
Give to general statements about leukocyte adhesion deficiency
- Failure to recognise activation markers expressed on endothelial cells
- Neutrophils are mobilised, but cannot exit bloodstream
Give a clinical feature of leukocyte adhesion deficiency
Recurrent bacterial and fungal infections
What is the blood count like in leukocyte adhesion deficiency?
Very high neutrophil counts
Where is the site of infection in leukocyte adhesion deficiency?
Deep tissues, N.B. no pus formation
What type of immunodeficiency is leukocyte adhesion deficiency?
Rare primary immunodeficiency
What type of genetic defect causes leukocyte adhesion deficiency?
Genetic defect in leuococyte integrins (CD18)
What does leucocyte adhesion deficiency result in?
Failure of neutrophil adhesion and migration
Name 3 direct recognition methods of the binding of a pathogen to a macrophage
- Lectin receptors
- TLRs
- Scavenger receptors
Name 2 microbial-specific structures that pathogen recognition receptors recognise
- Bacterial sugars
2. Lipopolysaccharide
What do pathogen recognition receptors exhibit?
Genetic polymorphism - some are associated with increased susceptibility to bacterial infection, but most do not cause significant disease
What is the name for molecules that act as binding enhancers for the process of phagocytosis?
Opsonins
Name 3 opsonins
- Complement C3b
- IgG
- C-reactive protein
Where do opsonins bind to?
Receptors on phagocyte surface
What do Fc receptors of phagocytes allow?
Binding of antibody that is also bound to antigen
What do phagocytes express which binds to complement fragments which are also bound to antigens?
Complement receptor 1 (CR1)
What may cause defective phagocytosis?
Defect in opsonin receptors
What type of defect will also result in decreased efficiency of opsonisation, as well as defect in opsonin receptors?
Any defect of complement or antibody production
When the complement or antibody production have defects, what type of defect of recognition is this classed as?
Functional defect of phagocytosis
What type of failure is involved in chronic granulomatous disease?
Failure of oxidative killing mechanisms
What three features lead to absent respiratory burst, which leads to failure of oxidative killing mechanisms?
- Deficiency of the intracellular killing mechanism of phagocytes
- Inability to generate oxygen free radicals
- Imparied killing of intracellular micro-organisms
What is the inability to clear organisms caused by in chronic granulomatous disease?
Excessive inflammation
What two features lead to excessive inflammation in chronic granulomatous disease?
- Failure to degrade chemoattractants and antigens
2. Persistent accumulation of neutrophils, activated macrophages and lymphocytes
In chronic granulomatous disease: failure of oxidative killing mechanisms - what does the inability to clear organisms ultimately result in?
Granuloma formation
Give 5 features of chronic granulomatous disease
- Recurrent deep bacterial infections
- Recurrent fungal infections
- Failure to thrive
- Lymphadenopathy and hepatosplenomegaly
- Granuloma formation
What 4 recurrent deep bacterial infections are especially prominent in chronic granulomatous disease?
Staphylococcus
Aspergillus
Pseudomonas cepacia
Mycobacteria, atypical mycobacteria
What investigation would you do for chronic granulomatous disease?
NBT (“nitroblue tetrazolium”) test
Give the three steps in the method for NBT testing in chronic granulomatous disease
- Feed patient neutrophils source of E.coli
- Add dye that is sensitive to H2O2
- If hydrogen peroxide is produced by neutrophils, due changes colour
Give two supportive treatment options for chronic granulomatous disease?
Prohpylactic antibiotics
Prophylactic antifungals
Give two definitive treatments for chronic granulomatous disease?
Stem cell transplantation
Gene therapy
What is special about these three intracellular organisms - Salmonella, Chlamydia, Rickettsia?
They hide from immune system by locating within cells
What is clever about the way mycobacteria species hide in the body?
They are intracellular organisms and hide within immune cells
What does an infection with mycobacteria (TB) activate?
IL-12 - gIFN network
What is the first step in IL-12 - gIFN network?
Infected macrophages stimulated to produce IL-12
IL-12 - gIFN network: after IL-12 has been produced by infected macrophages, what occurs?
IL-12 induces T cells to secrete gamma interferon (gIFN)
During IL-12 - g-IFN network - what occurs after T cells have secreted gIFN?
gIFN feeds back to macrophages and neutrophils
During IL-12 - gIFN network: what occurs after gIFN has fed back to macrophages and neutrophils?
It stimulates the production of TNF
During IL-12 - gIFN network: what occurs after the production of TNF?
TNF activates NADPH oxidase which stimulates oxidative pathways
Give 3 single gene defects in the IL-12 - gIFN axis?
gIFN receptor deficiency
IL-12 deficiency
IL-12 receptor deficiency
Name an important side effect of anti-TNF therapy?
Reactivation of latent tuberculosis
Name the two phagocyte recruitments
- Mobilisation from bone marrow
2. Migration to site of infection
How would you investigate the phagocyte recruitment: mobilisation from bone marrow?
Full blood count and differential
How would you investigate phagocyte recruitment: migration to site of infection?
Presence of pus, expression of neutrophil adhesion molecules
How would you investigate chemotaxis and endocytosis in phagocyte function?
Chemotactic assays
How would you investigate the formation of phagolysosomes in phagocyte function?
Phagocytosis assays
How would you investigate oxidative killing in phagocyte function?
NBT test of oxidative killing
What are is the neutrophil count, pus formation, leukocyte adhesion markers and nitroblue test of oxidative killing (NBT) like in congenital neutropaenia?
Neutrophil count - absent
Pus formation - No
Leukocyte adhesion markers - Normal
NBT - usually absent (because no neutrophils)
What are is the neutrophil count, pus formation, leukocyte adhesion markers and nitroblue test of oxidative killing (NBT) like in leukocyte adhesion defect?
Neutrophil count - Increased during infection
Pus formation - No
Leukocyte adhesion markers - Absent
NBT - Normal
What are is the neutrophil count, pus formation, leukocyte adhesion markers and nitroblue test of oxidative killing (NBT) like in chronic granulomatous disease?
Neutrophil count - normal
Pus formation - yes
Leukocyte adhesion markers - normal
NBT - abnormal
What two ways can phagocyte deficienceies be treated?
Aggressive management of infection
Definitive therapy
In aggressive management of phagocyte deficiencies, what two drugs are used in infection prohpylaxis?
Septrin
Itraconazole - antifungal
In the aggressive management of infection in phagocyte deficiencies, what other than infection prophylaxis, can be used for treatment?
Oral/intravenous antibiotics
Surgical draning of abscesses
Give two definitive therapies for treatment of phagocyte deficiencies?
Bone marrow transplantation
Specific treatment for Chronic granulomatous disease - gamma interferon therapy/gene therapy
What is severe congenital neutropaenia and cyclic neutropaenia caused by?
Failure of neutrophil differentiation
What does failure to express leukocyte adhesion markers give rise to?
Leukocyte adhesion deficiencies
What disease results from failure of oxidative killing?
Chronic granulomatous disease
What does a failure of cytokine production lead to?
gIFN and IL-12 deficiency
What type of response is the recognition by preformed, non-specific effectors via pattern recognition molecules. Recruitment and activation of phagocytes and complement?
Innate immune response
What do migrating dendritic cells initiate?
Adaptive immunity
What immunity is responsive to an unlimited number of molecules, has specificity and memory and its repertoire is not genetically encoded?
Acquired
What two organs beginning with ‘a’ are involved in the aquired immune response?
- Adenoid
2. Appendix
What three anatomical parts are involved in the aquired immune response, beginning with “t”?
Tonsil
Thymus
thoracic duct
Which two veins are involved in the squired immune response?
Subclavian vein (left and right)
Which three anatomical parts beginning with “L” are involved in the adaptive immune response?
Lymph nodes
Lymphatics
Large intestine
Is bone marrow part of the anatomy of the acquired immune response?
Yes
Which anatomical part beginning with “p”, “k”, “h” and “s” are involved in the acquired immune response?
Peyer’s patch in the small intestine
Kidneys
Heart
Spleen
Where do T lymphocytes arise from?
Haematopoetic stem cells in bone marrow
Where are immature T cells exported to from the bone marrow?
To the thymus for proliferation and maturation
What percentage of T cells survive selection in the thymus?
10%
Once mature T lymphocytes have entered the circulation, where do they reside?
In lymph nodes and secondary lymphoid follicles
What cells provide defence against intracellular pathogens and viruses and immunoregulation?
T lymphocytes
What are the two main groups of T cells?
CD4 and CD8 (each with different function and different expression of cell surface proteins
Which type of T cells have immunoregulatory functions and provide costimulatory signals?
CD4+
What two roles do the costimulatory signals from CD4 T cells have?
- Necessary for activation of CD8 T lymphocytes nad naive B cells
- Also influence phagocyte function
Other than providing costimulatory signals, what do CD4 T lymphocytes produce and regulate?
Produce cytokines
Regulate other lymphocytes and phagocytes
Which type of T cell recognises peptides presented on HLA class II molecules?
CD4+ T lymphocytes
Which thee peptides in association with HLA class I do CD8+ cells recognise?
HLA-A
HLA-B
HLA-C
In what three ways do cytotoxic T cells kill other cells directly?
Production of pore-forming molecules: perforin
Triggering apoptosis of the target
Secrete cytokines e.g. IFNgamma
Name a production of pore-forming molecules used by T cells to kill cells?
Perforin
Where do B cells arise from?
Haemopoetic stem cells in bone marrow
Where are mature B lymphocytes mainly found?
In bone marrow, lymphoid tissue, spleen
What two functions fo B cells have?
Antibody production
Antigen presentation
What are the 4 changes of B cell in development in the bone marrow?
- Stem cells
- Lymphoid progenitors
- Pro B cells
- Pre B cells
What do Pro B cells express?
IgM
What do pre B cells express?
IgM and IgD
What four other cells can IgM B cells go on to mature into?
IgM plasma cells
IgA
IgE
IgG
Where do antigen encounters with B cells occur?
Within lymph nodes
What do B cells within the lymph nodes need to rapidly proliferate?
Appropriate signals from T lymphocytes
What is meant by B cells undergoing highly complex genetic rearrangements?
Generate B cells that express receptors of greater affinity than the original
What two cells can T cell stimulated B cells further differentiate into?
Long-lived memory cells
Plasma cells which produce antibody
Give four functions of antibodies
- Identification of pathogens
- Rcruitment of other componenets of immune response to remove pathogens
- Neutrilisation of toxins
- Particularly important in defence agaisnt bacteria of all kinds
What three componenets of immune response can antibodies recruit?
Complement
Phagocytes
NK cells
What is a defect of haemopoetic stem cells called, that makes the adaptive immune response go wrong?
Reticular dysgenesis
What leads to the failure of production of Neutrophils, Lymphocytes, Monocytes/macrophages, platelets and is fatal unless corrected with bone marrow transplantation?
Recticular dysgenesis
What disease is associated with failure of production of lymphocytes?
Severe combined immunodeficiency
How long before a patient with severe combined immunedeficiency becomes unwell?
3 months of age
Do you get persistent diarrhoea with severe combined immunodeficiency?
Yes
What significant clinical feature is present in severe combined immunodeficiency?
Graft versus host disease (skin disease)
What does colonisation of infants “empty” bone marrow by maternal lymphocytes cause?
Graft versus host disease
Which antibody can cross the placenta?
IgG
Between 0 months and 6 months, where does the neonate get IgG from?
Colostrum and breast milk
What is SCID?
Severe Combined Immuno Deficiency
What protects the SCID neonate in the first 3 months of life?
Maternal IgG
What is the term for normal babies getting infections at 3-4 months if their immune systems are slow to mature?
Transient hypogammaglobulinaemia of infancy
Name 4 pathways which can cause severe combined immunodeficiency
- Deficiency of cytokine receptors
- Deficiency of signalling molecules
- Metabolic defects
- Defective receptor arrangements
What is the commonest form of Severe combined immunodeficiency?
X-linked SCID
What is the mutation in X-linked SCID?
Mutation of componenet of IL-2 receptor
What receptor is shared by many other cytokine receptors?
IL-2 receptor
Which mutation in X-linked SCID results in inability to respond to cytokines and what two things does this lead to?
Mutation of componenet of IL-2- receptor
Failure of T cell and NK cell development
Production of immature B cells
What can be said about the T cell number, B cell number and development of lymphoid tissue and thymus in X-linked SCID?
T cells - very low or absent
B cells - normal or increased
Poorly developed lymphoid tissue and thymus
What are 3 methods of prophylactic treatment for SCID?
- Prophylactic antibiotics and antifungals
- Aggressive treatment of exisiting infections
- Antibody replacement - IV immunogloblin
Give two definitive treatments for SCID involving stem cells
- Stem cell transplant from HLA identical sibling if possible
- Stem cell transplant from other sibling or parent, or from matched unrelated donor
In gene therapy for SCID: can Stem cells be treated ex vivo to express the missing component?
Yes
What is DiGeorge syndrome?
Developmental defect of 3rd/4th pharyngeal pouch
What chromosome is deleted in DiGeorge syndrome?
22q11
What is CATCH-22 for DiGeorge syndrome?
C - Cardiac defects A - Abnormal facial features T - Thymus underdevelopment C - Cleft palate H - Hypocalcemia 22 - Deletion of several genes in chromosome 22
What disease does a funny looking kid with: low set ears, abnormally folded ears, high forehead, cleft palate, small mouth and jaw, hypocalacemia, oesophageal atresia, T cell lymphopenia and complex congenital heart disease have?
DiGeorge Syndome
What does failure of thymic development in DiGeorge syndrome result in?
T cell immunodeficiency (nowhere for T cells to mature)
In DiGeorge syndrome, what comes before Hypocalcaemia?
Hypoparathyroidism
Which two developmental disorders can DiGeorge sybndrome cause?
Obsessive compulsive disorder
Schizophrenia
Which gene is responsible for embryonic development of the pharyngeal pouch?
TBX1
Name three types of infections someone with DiGeorge will get?
Recurrent viral infections
Recurrnet bacterial infections
Frequent fungalo infecitons
In a laboratory investigation of DiGeorge syndrome - what can be said about: T cell number and activation response, B cell numbers and antibody responses and NK cell numbers?
T cells - absent or decreased, defective T cell activation response
B cells - normal or increased, low IgG, IgA, IgE, poor antibody responses to specific pathogens
Normal NK numbers
With DiGeorge syndrome, what happens to T cell function through ageing?
Improves
What 4 things can be done as management for DiGeorge syndrome?
Correct metabolic/cardiac abnormalities
Prophylactic antibiotics
Early and aggressive treatment of infection
Some patients require immunoglobulin replacement
What three features can disorders of T cell effector function affect?
Cytokine production
Cytotoxicity
T-B cell communication
What does deficiency of any componenet of cytokine production (T cell effector function) result in?
Susceptibility to infection such as TB, BCG, Aspergillus
What disease is failure of lymphocyte precursors?
SCID
What disease involves failure of thymic development?
DiGeorge syndrome
What disease involves failure of expression of HLA molecules?
Bare lymphocyte syndromes
What two deficiencies are associated with failure of signalling, cytokine production and effector functions?
gIFN deficiency and IL-12 deficiency
What disease is associated with failure of normal apoptosis?
Autoimmune lymphoproliferative syndromes
What are recurrent infections (viral, fungal, bacterial, intracellular), opportunistic infections, malignancies young and autoimmune disease all clinical features of?
T cell deficiencies
What are the 3 first line investigations for T cell deficiencies?
- Total WCC and differential
- Serum immunoglobulins and protein electrophoresis - surrogate marker of functional T cells
- Quantification of lymphocyte subpopulations
What are the 3 second line investigations for T cell deficiencies?
- Functional tests of t cell activation and proliferation - may be useful if signalling or activation defects are suspected
- Additional tests of lymphocyte lineage
- An HIV test is essential
Are lymphocyte counts higher in children or adults?
Children
If a patient is getting recurrent upper and lower respiratory tract infections, recurrent GI infections, often common organisms what is going on?
Antibody deficiency
Name 2 antibody mediated autoimmune diseases?
- Idiopathic thrombocytopaenia
2. Autoimmune haemolytic anaemia
What occurs when there is failure to produce mature B cells (Pro B cells cannot make Pre B cells)?
Bruton’s X-linked hypogammaglobulinaemia
What disease is there no circulating B cells, no plasma cells and no circulating antibody after the first 6 months?
Bruton’s X-linked hypogammaglobulinaemia
What is the prevelance for selective IgA deficiency?
1:600
What disease has low IgG, IgA and IgE, recurrent bacterial infections, cause and mechanism is unknown and often associated with autoimmune disease?
Common variable immuno deficiency
In common variable immune deficiency - what three immunoglobulins are low?
IgG, IgA, IgE