Immunology Flashcards
What is the acronym ACID with regard to types of hypersensitivity reactions?
A - anaphylactic, allergic, atopic
C - cell-mediated, cytotoxic
I - immune complexes
D - delayed
With regard to HLA, which are up-regulated and which are down-regulated in pregnancy?
Down-regulated = HLA-A and HLA-B Up-regulated = HLA-E and HLA-G
How does the placenta inhibit complement protein?
DAF, MCP and CD59 expressed on the placenta inhibit complement proteins
With regard to T-helper (Th) cells, which increase and which decrease in pregnancy?
Th1 = decreased, therefore rheumatoid improves in pregnancy Th2 = increased, therefore SLE exacerbated during pregnancy
Which Ig has a pentameter structure?
IgM
Which Ig’s have a monomer structure?
IgA, IgD, IgG, IgE
Which Ig has a dimer structure?
IgA - can have either a dimer or monomer structure
What are the 3 professional APC’s?
1) Dendritic cells
2) Macrophages
3) B-cells
Following potentially sensitising events, when should anti-D Ig be administered?
As soon as possible, always within 72 hours
When is anti-D Ig prophylaxis indicated at <12/40 gestation?
1) Ectopic pregnancy
2) Molar pregnancy
3) TOP
4) Uterine bleeding which is repeated and heavy or associated with abdominal pain
What are the potentially sensitising events beyond 12/40 gestation that require anti-D?
1) Amniocentesis
2) CVS
3) APH and PV bleeding
4) ECV
5) Abdominal trauma
6) Ectopic
7) Evacuation of molar pregnancy
8) IUD/stillbirth
9) Miscarriage
10) TOP
11) Delivery
12) In-utero interventions, e.g. surgery, lasers etc.
Which Ig crosses the placenta?
IgG
Which Ig is the first to be produced by the neonate?
IgM
Which Ig is passed through breast milk?
IgA
What are the common products of the the 3 complement pathways?
C3, cleaved to C3a and C3b
What is the role of C3b?
1) Opsonisation
2) Forms C5 convertase (with other proteins) which cleaves C5 to C5a and C5b
What does C5b do?
Recruits C6, C7, C8 and C9 to form MAC - membrane attack complex
What is an allograft?
An allograft is where tissue from a different individual of the same species is used - i.e. a foetus is a natural allograft
At what gestation does maternofetal IgG start?
Week 12
At what gestation does the fetus start producing IgM?
Weeks 10-11
What does Th1 produce?
TNF-alpha, IFN-y and IL-2 - therefore since Th1 is suppressed in pregnancy, these are all reduced during pregnancy
What does Th2 produce?
IL-4, IL-5, IL-9, IL-10 and IL-13 - since Th2 production increases during pregnancy, these also increase during pregnancy
What are some examples of attenuated vaccines?
1) MMR
2) Polio
3) BCG
What are some examples of inactivated vaccines?
1) Hep A
2) Pertussis
3) Influenza
What are some examples of toxoid vaccines?
1) Tetanus
2) Diptheria
What is an example of a subunit vaccine?
Hep B
What are examples of a type III hypersensitivity reaction?
1) SLE
2) Serum sickness
3) RA
4) Extrinsic allergic alveolitis
5) Post-strep glomerulonephritis
What is the innate immune system?
The immediate and non-specific response to attack
What is the adaptive immune system?
The more complex and specific response to antigens and generates immunological memory
What are the cells of the innate immune system?
Macrophages, neutrophils, natural killer cells
What are the cells of the adaptive immune system?
T-helper cells, B cells
What is the role of IgE?
Activates mast cells
At what gestation should a pregnant woman receive her whooping cough vaccination?
27-36 weeks
What are some examples of type I hypersensitivity reactions?
Anaphylaxis, atopy, allergic asthma
What are type I hypersensitivity reactions caused by?
IgE mediated degranulation of mast cells, triggered by antigen binding. Effects in <30 mins
What are some examples of type II hypersensitivity reactions?
Transfusion reaction, rhesus incompatibility
What are type II hypersensitivity reactions caused by?
Cytotoxic. Antigens cause IgM and IgG formation which bind to surface of target cells and then destroy it by complement. Effects 5-12 hours
What are type III hypersensitivity reactions caused by?
Immune-complex mediated. Effects 3-8 hours
What are some examples of type IV hypersensitivity reactions?
Contact dermatitis, chronic transplant rejection
What are type IV hypersensitivity reactions caused by?
Delayed. T-helper cells release cytokines leading to macrophage and T cell accumulation. Effects 24-48 hours
On which chromosome are the HLA genes found?
Chromosome 6
What are the most efficient antigen-presenting cells (APC)?
Dendritic cells
What are the different types of APCs?
Dendritic cells and macrophages
From what and where are APCs derived?
Derived from monocytes produced by bone marrow
What are some examples of type V hypersensitivity reactions?
Myasthenia gravis
Graves disease
Which hypersensitivity reaction forms the basis of the Mantoux test?
Type IV
What type of vaccine is varicella?
Attenuated
Which Ig has the highest molecular weight?
IgM
What is the mechanism of action of azathioprine?
Inhibition of nucleic acid synthesis in all mitotic cells
Natural killer cells belong to what cell type?
Lymphocytes
What 2 inflammatory mediators are released by both mast cells and platelets?
Histamine and serotonin
What is the frequency of of lupus anticoagulant Abs in the general population?
2-5%
What is the risk of fetal mortality with lupus anticoagulant Abs?
85-95%
What type of cell congregates around the cervix to release collagenase?
Neutrophils
What is the most abundant circulating phagocyte?
Neutrophils
What are the two different receptor types found on the surface of NK cells?
- CD16 receptors
2. KIRs (i.e. killer cell immunoglobulin-like receptors) - they engage MHC molecules on target cells
What are the three pathways that can activate complement?
- Classic pathway
- Alternative pathway
- Lectin pathway
What are the two different types of CD4+ T cells?
Th1 and Th2
What are the different types of cytokine?
- Interferons
- Interleukins
- Chemokines
- Growth factors
What is an autograft?
Tissue transferred from one part of the body to another
What is an isograft?
Tissue transferred between genetically identical individuals
What is a xenograft?
Tissue transferred between two different species
What are some examples of type III hypersensitivity reactions?
Persistent infection - e.g. le/prosy, viral hepatitis
Immune-mediated - e.g. SLE and RA
Inhalation of antigen - e.g. farmer’s lung, pigeon-fancier’s lung
Rhesus D immunoglobin treatment utilises what class of antibody?
IgG
Which is the only live vaccine recommended for people with HIV?
Measles
Where in the body do T cells differentiate?
Thymus
What does the Fab segment of the immunoglobulin determine?
Affinity/specificity of antibody for antigen
What does the Fc segment of the immunoglobulin determine?
All other properties, e.g. ability to cross the placenta etc.
Which immunoglobulin has the lowest molecular weight?
IgG
What is the volume of a unit of packed red cells?
280+/-20ml
What are the two arms of the adaptive immune system?
- Humoral immunity - antibody production
2. Cellular immunity
What are the three types of immune tolerance?
- Central tolerance
- Peripheral tolerance
- Acquired tolerance
Where does central tolerance occur?
Bone marrow and thymus
What type of immune tolerance occurs in pregnancy?
Acquired tolerance
Where is the complement system synthesised?
Liver
What is the cause of hyperacute transplant rejection?
Pre-formed host antibodies (hence why it occurs so quickly)
What is the trigger of the classical complement pathway?
Antibody trigger
What is the trigger of the alternative complement pathway?
Antigen trigger
What is the function of CRP?
It coats a pathogen to promote opsonization
Its gene is on chromosome 1
What are the 3 types of lymphocytes?
- T cells
- B cells
- NK cells
What are the different types of T cells?
- CD4 expressing T cells - i.e. Th1 and Th2 cells (MHC 2 only)
- CD8 expressing T cells - i.e cytotoxic and suppressor T cells (MHC 1 only)
- CD4 and CD8 expressing T cells
Which part of the adaptive immune system do Th1 cells mediate?
Cellular immunity
Which part of the adaptive immune system do Th2 cells mediate?
Humoral immunity
What do B cells differentiate into?
Plasma cells - secret antibodies
Memory cells
What is contained within a lymph node cortex?
Outer (nodular) cortex - contains B cells
Inner (juxtamedullary) cortex - contains T cells
What is contained within a lymph node medulla?
Medullary cord - contains plasma and T cells
Medullary sinuses - contains histiocytes and reticular cells
What is the structure of immunoglobulins?
2 heavy and 2 light chains bound by disulphide bonds
What proportion of fetuses develop congenital heart block in the presence of anti-Ro/La positive mothers?
2% - permanent
What proportion of fetuses develop cutaneous neonatal lupus in the presence of anti-Ro/La positive mothers?
5% - transient
What is the perinatal mortality rate of congenital heart block?
19%
Which markers may indicate ovarian sex cord stromal tumours?
Calretinin
Inhibin
Which markers may indicate mucinous ovarian tumours?
Ca 19-9
CK20
What is responsible for the destruction of the myelin sheaths seen in MS?
Cellular immunity - Th1 cells
What are the 2 immunological interfaces in human pregnancy?
- Extra-villous cytotrophoblast/decidua - in early pregnancy
- Syncytiotrophoblast/maternal blood - in late pregnancy
What are the immunological characteristics of the syncytiotrophoblast?
- NO MHC1 or MHC2 antigens expressed
- NO stimulation of cytotoxic activity
- NO NK cell activity
When does maternal IgG transfer to fetus peak?
32 weeks
