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Immunology Flashcards

1
Q

What factors make up the adaptive immune system?

A

B lymphocytes

T lymphocytes

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2
Q

What are categories of primary immunodeficiency?

A 
Phagocyte deficiencies (innate cell-mediated immunity)
Complement deficiencies (innate humoral immunity)
Severe combined immuno-deficiencies (adaptive cell-mediated 
immunity)
Predominantly antibody deficiencies (adaptive humoral immunity)
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3
Q

What are categories of secondary immunodeficiency?

A

Hyposplenism / Asplenism
Haematological malignancies
HIV / AIDS

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4
Q

What can cause Immunosuppression?

A 
Steroids & other immunosuppressive drugs
Cytotoxic chemotherapy (for malignancies)
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5
Q

What factors make up the innate immune system?

A 
Epithelial barriers
Phagocytes
Dendritic cells
Complement 
Acute phase proteins
NK cells
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6
Q

What is Chronic Granulomatous Disease (CGD)?

A

Multiple possible defects (most frequently X-linked)
Phagocytes unable to destroy ingested microbes due to a lack of oxidative burst to produce free radicals
Excessive granuloma formation occurs instead

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7
Q

What are clinical features of chronic granulomatous disease?

A

Eecurrent & persistent infections: pneumonia, skin infections, abscesses (skin & internal), septic arthritis and osteomyelitis

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8
Q

What investigations can be used to diagnose chronic granulomatous disease?

A

Nitroblue-tetrazolium (NBT) test: microscopy (normal phagocytes reduce NBT to a dark pigment)
Dihydrorhodamine (DHR) test: flow cytometry (normal phagocytes reduce DHR to a fluorescent pigment)
Genetic analysis to identify exact genetic defect

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9
Q

What are treatment options for chronic granulomatous disease?

A

Early diagnosis and treatment of any infections
Prophylactic antibiotics (co-trimoxazole and imidazoles)
Recombinant IFN-gamma (70% less infections)
Bone marrow / stem cell transplantation (curative)

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10
Q

Describe the process of phagocytosis

A

Chemotaxis and adherence of microbe to phagocyte
Ingestion
Formation of a phagosome
Fusion of phagosome with a lysosome to form phagolysosome
Digestion of ingested microbe by enzymes
Formation of residual body containing indigestible material
Discharge of waste materials

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11
Q

What is Common Variable Immunodeficiency (CVID)?

A

Multiple possible defects (not X-linked)
Hypogammaglobulinaemia (IgG, usually IgA, possibly IgM)
Lack of antibodies to neutralise & opsonise pathogens
Severe, persistent, unusual and recurrent infections, autoimmune, malignant, enteric and lymphoid disorders

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12
Q

What are clinical features of common variable immunodeficiency?

A

Streptococcus pneumoniae (LRTIs and sepsis)
Haemophilus influenzae (URTI/LRTIs and meningitis)
Neisseria meningitidis (meningitis)
Otitis media (Pseudomonas)
Bronchiectasis
Sever, persistent, unusual or recurrent infections

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13
Q

What investigations can be done to diagnose common variable immunodeficiency?

A

Reduced immunoglobulins on simple blood test
Decreased IgG always, deceased IgA usually, decreased IgM in ~50%
Normal B lymphocyte count, but immature types

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14
Q

What are treatment options for common variable immunodeficiency?

A

Early diagnosis and treatment of any infections
Prophylactic immunoglobulin transfusions (IV every 3-4 weeks or SC every week) immunoglobulin reactions can occur (serum sickness)

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15
Q

What is serum sickness?

A

Flu-like symptoms (but no respiratory component)
Possible thrombotic events or anaphylaxis
Reaction to immunoglobulin treatment

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16
Q

What can be causes of Hyposplenism or asplensim?

A

Congenital
Post-surgical (after trauma)
Atrophy (after infarcts from thrombosis or sickle cell disease)
Functional (malignancy, coeliac disease or IBD)

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17
Q

What is the risk with hypo/asplensim? Which groups of people are at particular risk?

A

Increased risk of severe infection with encapsulated bacteria Strep. pneumoniae, H. influenza, N. meningitides)
Higher risk of malaria and babesiosis
Age 50, poor response to vaccination, previous invasive pneumococcal infection, haematological malignancy, other immunosuppression

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18
Q

What are clinical features of Hyposplenism?

A

Respiratory tract infection possibly with sepsis

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19
Q

What investigations can be done to diagnose Hyposplenism?

A

Spleen function assessed by imaging (USS)

Blood films show Howell-Jolly bodies in erythrocytes (Nuclear DNA Remnants)

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20
Q

What are treatment options for Hyposplenism?

A

Prevention with vaccination & antibiotics
UK Green Book (Immunisation against Infectious disease)
Pneumococcal, Hib, meningococcal and flu vaccines (with measurement of serological response)
Phenoxymethlypenicillin (oral) if high-risk
Strict malaria prophylaxis and bite avoidance measures
Patient education on early treatment of infections

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21
Q

What is HIV?

A

Aquired through sex, blood transfusions, iatrogenic
Infects Th lymphocytes (CD4 cells)
CD4

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22
Q

What are clinical features of HIV/AIDS?

A 
Non-specific seroconversion illness after 2-4 weeks
Latency for ~10 years before AIDS develops
Cerebral toxoplasmosis
PML (progressive multi focal leukoencephalopathy) due to JC virus
HSV ulcers (chronic)
Pneumocystis pneumonia (recurrent)
Tuberculosis
Intestinal cryptosporidiosis
Cryptococcal meningitis
CMV retinitis
Oesophageal candidiasis
Pneumococcal pneumonia 
Atypical mycobacterial infection
Intestinal isosporiasis
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23
Q

What investigations can be done to diagnose HIV?

A

Low lymphocytes / high immunoglobulins
HIV tests (serology & antigen-detection)
CD4 count / HIV viral load

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24
Q

What are treatment options for HIV?

A

Initially targeted at opportunistic infections
Prophylaxis against infections where possible (eg. toxoplasmosis, cryptococcosis, pneumocystis pneumonia, mycobacterium avium complex)
Anti-retroviral combination drugs, typically 3-4 given for life

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25
What is the prognosis of HIV and AIDS?
AIDS without treatment: death in 1-3 years | HIV with treatment: almost normal life expectancy
26
What are clinical features of Immunosuppression caused by steroids and other drugs?
All cause risk of new infections Steroids: risk of CMV reactivation Methotrexate, azathioprine, cyclosporine: increase risk of lymphoma Anti-TNF drugs: re-activation of TB
27
What is neutropenic sepsis?
Development of fever, often with other signs of infection in a patient with an abnormally low neutrophil count Absolute neutrophil count
28
What molecules are involved in neutrophil recruitment to a site of injury?
Selectins on neutrophils and endothelium allow rolling | At sites of injury, integrins are expressed and cause adhesion of the neutrophils
29
What organisms can cause neutropenic sepsis?
Bacteria: Staph aureus, E. Coli, Pseudomonas aeruginosa Fungi: after prolonged neutropenia, Difficult to diagnose, Antifungals added if fever does not respond to antibiotics
30
What is the empirical treatment for neutropenic sepsis?
Tazobactam-piperacillin (Tazocin) Vancomycin (If no response at 48 hours and lines in) Antifungal: Voriconazole/Amphotericin B (If no response at 72 hours)
31
20 year old, lots of chest infections as a child, was tested for cystic fibrosis – neg, Bad acne as a teenager, Recurrent skin abscess. Chronic cough, Persistent lymphadenitis. Burkholderia cepacia infection isolated. DHR not oxidised by neutrophils, so no shift in DHR fluorescence. What is the likely diagnosis?
Chronic granulomatous disease
32
What can be common causative organisms and clinical manifestations in chronic granulomatous disease?
Recurrent bacterial infections: Pneumonia, Abscesses, Lymphadentiis, Osteomyelitis, Bacteraemia Predominant organisms: Staphylococcus aureus, Burkholdia (Pseudomonas) cepacia, Serratia marcescens
33
23 yr old woman has everal episodes of pneumococcal pneumonia and sinusitis. She has seronegative polyarthritis, chronic intermittent diarrhoea but colonoscopy normal. Low levels of IgG and IgA, what is the likely diagnosis?
Common variable immunodeficiency
34
What are clinical manifestations of common variable immunodeficiency?
``` Infections Hematologic or organ-specific autoimmunity Chronic lung disease Bronchiectasis Gastrointestinal inflammatory disease Malabsorption Granulomatous disease Liver disease/hepatitis Non Hodskins Lymphoma Other cancers ```
35
What infections may be common in someone with common variable immunodeficiency?
Sino-pulmonary: Bacterial (pneumococcal, haemophilus) Chronic giardia Infective complications of chronic lung diseases: Bronchiectasis, obstructive airways disease
36
35 year old woman, Cough and shortness of breath, No response to course of amoxicillin, seen by dermatology for dermatitis, Referred to haem because of persistent lymph nodes O2 sats – 94% fall to 82% on climbing stairs, WCC normal, CRP 65, CD4 count 12, Sputum – Pneumocystis jirovecii PCR pos. What is the diagnosis?
HIV
37
What investigations should be used to identify common immunodeficiencies?
Full blood count Immunoglobulins Serum complement HIV testing
38
What phases do T cells go through from being immature to maintenance?
Initiation: APC presents antigen to T cell Clonal expansion Contraction Maintenance
39
By what mechanism do B cells adapt to recognise new antigens?
Somatic hypermutation Programmed process of mutation affecting variable regions of immunoglobulin genes but only affects individual immune cells
40
What are immature B cells called?
Centroblasts Which become centrocytes Which become plasma cells or memory B cells
41
Where are the antigens which b and T cells target?
B cells: extracellular | T cells: intracellular
42
What types of immunosuppressive drugs are there?
Corticosteroids Cytotoxic drugs T cell suppressant Antibody/biologics
43
What is membranous glomerulonephritis?
Commonest in adult Autoantibodies against the phospholipase A2 receptor 1 in the basement membrane Immune complex formation in the glomerulus Triggers membrane attack complex on glomerular epithelium causing it to become leaky
44
What is minimal change disease?
``` Commonest in children T / B cell dysfunction Glomerular permeability factor Proteinuria and oedema Lacks evidence of pathology on light microscopy ```
45
What is the first line treatment for minimal change disease? And how does it work?
Prednisolone: inhibitors transcription factors so reduced cytokine production, therefore reduced clonal expansion of t helper cells Ubiquitous expression of corticosteroid receptor Interrupts multiple steps in immune activation Inhibit antigen presentation (Innate) Inhibit cytokine production and proliferation of lymphocytes (Adaptive)
46
What are some autoimmune indications for plasma exchange?
Severe vasculitis Good pasture’s disease: antibodies attack basement membrane in lungs and kidneys Gillian Barre syndrome: antibodies against myelin/nerve axons in PNS Myasthenia gravis: antibodies against ACh receptor Antibody mediated transplant rejection
47
What are Sirolimus and Everolimus? And what is their mechanism of action?
mTOR inhibitors Block cell cycle progression in G1 Blocks IL2 mediated activation of T & B cells Reduced clonal proliferation of T cells
48
What are side effects of mTOR inhibitors?
Hypertriglyceridaemia Hypercholesterolaemia Pneumonitis Oral ulcers
49
What are advantages of mTOR inhibitors?
Reduce cancer risk | Not nephrotoxic
50
What is Rituximab and what is its mechanism of action?
Monoclonal antibody against surface determinant on B-cells (CD20) B cell depletion
51
What are side effects of Rituximab?
Neutropenia Hypogammaglobulinemia Reactivation of latent infections
52
What is alemtuzumab?
Monoclonal antibody to cell determinant CD52 | T cell depletion
53
What are side effects of alemtuzumab?
Leukopenia | Infection
54
What is infliximab? What is its mechanism of action?
Antibody against TNF-alpha Reduction of pro-inflammatory cytokines, leukocyte migration and activation Subsidence of inflammation
55
What are side effects of infliximab?
``` Infusion reactions Neutropenia Infections (TB) Demyelinating disease Heart failure Cutaneous reactions Malignancy Induction of autoimmunity ```
56
In what conditions might you use infliximab as treatment?
RA, IBD, Psoriasis and Ankylosing spondylitis
57
What is Behçet's disease?
Immune mediated small vessel systemic vasculitis Mucous membrane ulceration and ocular problems Recurrent oral aphthous ulcers, genital ulcers, uveitis
58
What is an antigen?
Substance capable of generating an immune response
59
What is immunological tolerance?
Unresponsiveness of immune system to an antigen, induced by previous exposure to that antigen
60
What is autoimmunity?
Immune response to self-antigens due to a failure of immunological tolerance
61
When specific lymphocytes encounter antigen for the first time they may be...?
Activated leading to an immune response | Inactivated or destroyed leading to tolerance
62
What is a tolerogen?
Antigen which induces tolerance
63
What is an immunogen?
Antigen which induces an immune response
64
What role does infection play in loss of immune tolerance?
Allows bystander activation of auto-reactive cells | Molecular mimicry
65
What fates do lymphocytes have which would react to self antigens in a healthy person?
Deleted Inactivated Undergo a change in their specificity
66
Where can self tolerance be induced?
Central: B cells in bone marrow, T cells in thymus | Peripheral
67
Describe central immunological tolerance to self antigens
Induced in immature lymphocytes in generative lymphoid organs. B cells in bone marrow, T cells in Thymus If cells react to self antigens: Apoptosis: Cell deletion Change in receptor until no longer self reactive (B Cells) Develop into regulatory T cells (CD4+ Cells), Mature and enter peripheral circulation, where peripheral tolerance will cause cell to undergo: anergy, deletion or suppression
68
Antigens that lymphocytes encounter in generative organs are...?
Self antigens | External antigens are not usually found in generative lymphoid organs but remain in peripheral lymphoid tissue
69
Describe peripheral immunological tolerance to self antigens
Mature lymphocytes Deletion: Induction of apoptosis in self-reactive lymphocytes Anergy: Render self-reactive lymphocytes incapable of reacting antigen upon re-exposure Suppression: T Regulatory Cells suppress self-antigen specific lymphocytes
70
Describe clonal deletion
CD4+ T cells which show high avidity self-reactivity are | negatively selected in the thymus
71
What are the determinants of negative selection in clonal deletion?
Presence or absence of self-antigen in thymus, determined by autoimmune regulator (AIRE) protein (transcription factor) whichcontrols expression of thymic epithelial cells which express tissue restricted antigens (major proteins from elsewhere in body) Affinity of T-Cell Receptor (TCR) for antigen. High affinity = increased chance deletion
72
What is anergy as a mechanism of peripheral tolerance?
Exposure of CD4+ T cells to antigen in absence of co- stimulation or innate immunity leads to CD4+ T cells becoming incapable of reacting to that antigen
73
What 2 signals are required for T cell activation? What happens if these are not present?
T cell receptor binding Ag presented on MHC Recognition of co-stimulators by CD28 If this is absent, prolonged stimulation by antigen will lead to anergy Co-stimulators are only expressed on antigen presenting cells when then are activated e.g. by innate immunity or inflammation
74
What are the 2 main inhibiting receptors which regulate T cell responses?
CTLA-4: Member of CD28 family, expression up-regulated in T cells exposed to antigen and terminates continued activation of these cells. Expressed on regulatory cells and mediates suppressive function. Acts to block T cell receptor signalling and reduce availability of co-stimulatory molecules on APC PD-1: Binds to ligand on APC and inactivates the T Cells
75
Where is CTLA 4 important in inhibiting T cells?
Centrally
76
Where is PD-1 important in inhibiting T cells?
Peripherally
77
What does suppression by regulatory T cells lead to inhibition of?
Effector T Cell production B Cell production NK Cell production
78
What does generation of regulatory T cells require?
Cytokines, especially Il-2 (promotes differentiation into T-regs)
79
What do regulatory T cells do?
Produce immunosuppressive cytokines Reduce ability of APCs to stimulate T Cells Consumption of Il-2 (necessary growth factor for other cell populations)
80
What are important factors in CD8+ T cell tolerance?
Co-stimulation presence or absence Inhibitory receptors: PD-1 T-Reg cells can control activation
81
By what processes does central B cell tolerance occur?
Deletion Receptor editing: non-self antigen specificity is reached Anergy: Occurs if cells recognise self-antigen weakly
82
By what processes does peripheral B cell tolerance occur?
In the absence of T Helper Cells Apoptosis Anergy (via engagement of inhibitory receptors)
83
What type of course do autoimmune diseases often follow?
Chronic, progressive, relapsing and remitting
84
What immune abnormalities can lead to autoimmunity?
Defective tolerance or regulation Abnormal display of self antigens Inflammation or an initial immune response
85
What abnormalities can occur, leading to defective tolerance or regulation?
``` Imbalance between lymphocyte activation and control due to: Defects in negative selection Defects in reg T cells Defects in apoptosis Inadequate function of inhibitory cells ```
86
What abnormalities might occur which result in an abnormal display of self antigens?
Increased expression Structural changes Exposure of hidden antigens
87
How can inflammation lead to autoimmunity?
Activate APC, therefore enabling co-stimulation and activation not anergy of self recognising lymphocytes
88
Describe autoimmunity as a polygenic multifactorial disease
Inheritance of multiple genetic polymorphisms contributing to susceptibility: Some disease specific, Some generic for autoimmune disease Contribution of variable environmental factors
89
Which autoimmune conditions are associated with HLA-B27?
Ankylosing spondylitis, reactive arthritis
90
Which autoimmune condition is associated with HLA-DR2?
Systemic lupus erythematosus (SLE)
91
Which autoimmune conditions are associated with HLA-DR3?
Atoimmune hepatitis, Sjögren’s syndrome, T1DM, SLE
92
Which autoimmune conditions are associated with HLA-DR4?
Rheumatoid arthritis, T1DM
93
What infections can trigger autoimmune conditions?
Streptococcal infection → rheumatic fever urethritis or gastroenteritis → reactive arthritis Campylobacter gastroenteritis → Guillain–Barré syndrome
94
How can infection lead to autoimmune conditions?
Molecular mimicry
95
What chemicals can lead to autoimmune disorders?
Anti-convulsants or antibiotics →drug-induced lupus | Halothane (general anaesthetic) →liver necrosis
96
What autoimmune condition can result from a teratoma?
Autoimmune encephalitis
97
Exposure of self antigens in which protected sites could lead to autoimmune destruction?
Eye | Testes
98
What is the significance of autoimmune conditions being mainly B cell mediated?
Easier to diagnose (eg. antibody detection tests) | Can occur in utero (eg. neonatal thyrotoxicosis, neonatal lupus)
99
What types of hypersensitivity reactions can cause autoimmune conditions?
Type 2: Antibody mediated e.g. Graves Type 3: Immune-complex mediated e.g. SLE Type 4: T-cell mediated
100
How can antibodies lead to autoimmune conditions?
Antibodies bind to antigens on cells: cause recruitment of inflammatory cells and tissue injury Can cause abnormal cellular function e.g. Graves’ Antigen-antibody complexes forming in circulation: induce vascular inflammation with ischaemia to associated tissue
101
How can immune complexes lead to autoimmune conditions?
Ag (self or foreign) and Ab complex deposit in tissues and induces inflammation Amount of complex deposited in a tissue is determined by nature of the complex and characteristic of the blood vessels
102
How can T cell mediated autoimmunity lead to disease?
Trigger inflammation leading to tissue injury
103
How can cytokines lead to autoimmune disease?
Immune-mediated inflammation (TH 1 and 17) via secretion of cytokines that recruit and activate leukocytes Delayed hypersensitivity: Activation of CD4+ T cells with inflammation 24-48 hrs after challenge
104
What would you measure levels of to confirm Graves' disease?
TSH receptor
105
What would you measure levels of to confirm Hashimoto's thyroiditis?
Thyroid peroxidase
106
What would you measure levels of to confirm Rheumatoid arthritis?
Rheumatoid factor
107
What would you measure levels of to confirm SLE?
ANA and dsDNA
108
What would you measure levels of to confirm Sjögren's syndrome?
ANA
109
What would you measure levels of to confirm Coeliac disease?
Anti-gliadin and anti-endomysial
110
What would you measure levels of to confirm Primary biliary cirrhosis?
ANA and AMA (anti mitochondrial antibodies)
111
What would you measure levels of to confirm chronic autoimmune hepatitis?
SMA (smooth muscle antibodies) and LKM-1 (liver kidney microsomal type 1)
112
What would you measure levels of to confirm Wegeners granulomatosis?
c-ANCA (anti neutrophil cytoplasmic antibody)
113
What is Wegeners granulomatosis?
Form of vasculitis that affects small vessels in organs | Lung and kidney damage
114
What are the most prevalent autoimmune conditions?
Graves' disease | Rheumatoid arthritis
115
What may be clinical features of anti phospholipid syndrome?
thrombophilia | recurrent miscarriages
116
List some symptoms of systemic lupus erythematosus
Systemic : malaise, fever, weight loss Skin : rash, photosensitivity, vasculitis, hair loss CNS : cerebral lupus, transverse myelitis Heart : pericarditis, Libman-Sacks endocarditis Lungs : pleural effusions, pulmonary fibrosis Kidneys : glomerulonephritis Blood : anaemia, leukopenia, thrombocytopenia, 2° anti phospholipid syndrome Other : 2° Sjögren's syndrome, arthralgia, non-deforming arthritis
117
Describe the pathogenesis of SLE
Susceptibility genes: b and T cells specific to self nuclear antigens External triggers: defective clearance of apoptotic bodies so increased burden of nuclear antigens Anti nuclear antibodies: form complexes which are endocytosed and stimulate B cells, resulting in high levels of anti nuclear IgG production
118
What investigations results would you expect in SLE?
FBC =↓Hb (chronic/haemolytic),↓WCC,↓Plts ESR : raised CRP : moderately raised ANA : 95% sensitivity dsDNA : 50% sensitivity & 99% specificity anti-cardiolipin (phospholipid) antibodies
119
What treatment is given for SLE?
Sun-avoidance / sun screens Steroids : as for other autoimmune rheumatological disorders NSAIDs : as for other autoimmune rheumatological disorders DMDs : hydroxychloroquine, azathioprine (anti-proliferative), cyclophosphamide (anti-proliferative) mAbs : rituximab (anti-CD20 on B lymphocytes)

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