Immunology Flashcards
What are the general ways to boost the immune system (4)
Vaccination
replacing missing components
Blocking immune checkpoints
Cytokine therapy
Briefly describe the adaptive immune response
The adaptive immune response consists of B and T cells, there is a wide repertoire of antigens receptors available from genetic recombination (SNPs, deletions etc).
There is a process of selection so that they are reactive enough but not autoreactive. Autoreactive antigens are deleted.
Upon detection of a specific antigen B cells undergo clonal expansion to produce effector (T cell-independent IgM secretion) cells and (germinal centre reaction to T cell-dependent )memory B cells -IgG, IgA and IgE. T cells will differentiate into effector cells to produce cytokines and cytotoxins
Which cells are antigen presenting cells?
Dendritic cells
Macrophages- Langerhans, Mesangial, Kupper cells, osteoclasts, microglia
B cells
Describe the formation and role of memory T cells
T cells are activated by antigen-presenting cells and undergo clonal (Cytokines are required for this usually from T helper cells - IL2. After expansion, many will apoptosis and some will survive as memory T cells - (Maintained by cytokines not antigen)
They have different surface proteins so can access non-lymphoid tissue (site of microbial entry).
More easily activated than naive cells
Explain the role of memory B cells
Survive a long time, rapid IgG response to antigen
Explain how the hemagglutinin is responsible for influenza infection and how the HA assay works
HA is responsible for the immune response against influenza and is one of the components of the flu vaccine.
In a red cells spot test- the red cells will clump together and form a red spot at the bottom. If HA is present the cells will bind to it and diffusely clump. If there is antigens to HA (eg vaccinated), this won’t happen and it will just look normal
Explain the role of the BCG and how the Mantoux test works
The BCG is a live attenuated vaccine, its purpose is to reduce the progression of TB rather than to stop primary infection.
The Mantoux test is injection of TB subdermal to check for an immune response (T4 response - T cell med)
What are the different types of vaccines (give examples)
Live attenuated (modified to limit pathogenesis)
-BCG, Polio (nasal), MMR, yellow fever, typhoid (oral), vaccinia
Inactivated and Component
-Inactivated:Flu, cholera, bubonic plague, Polio (salk- IM), Hep A, pertussis, Rabies
-Component: Hep B, HPV (capsid), Flu (neuraminidase and HA)
-Toxiods- inactivated toxins- diphtheria, tetanus
mRNA
-Sars-cov2
Dendritic - in dev for prostate cancer -tumour antigens as vaccines
What are the pros and cons of
a. live attenuated vaccines
b. inactive/ component
c. DNA vaccines
d. mRNA vaccines
a. + Mild symptomatic infection, broad immune response to lots of antigens (good strain coverage), long-lasting immunity, activates all phases of immune response
- Storage issues, Can revert to wild type pathogens, spread to contacts (ie they haven’t consented to be vaccinated) unsuitable for immunocompromised patients.
b. + safe for immunocompromised patients, easy storage, cheaper, no mutations
- less long-lasting and may need to be frequently updated, may need adjuvants, may be poorly immunogenic
c. +safe for immunocompromised patients, the potential for cancer vaccines
- expensive to store
Explain the role of conjugate vaccines and give examples
Conjugate vaccines.
Contain a polysaccharide + a protein carrier (the polysaccharide promotes a B cell response (transient), the protein carrier promotes T cell response.
-eg HiB, meningococcus, pneumococcus
What is the most common adjuvant and what are its proposed mechanisms of action
Aluminium salt - as it’s very safe and effective
- slow down antigen release= continual stim
- inflam reaction
- Activates Gr1 , IL4 and eosinophils -prime B cells
Name two experimental adjuvants
ISCOMS- immune-stimulating complexes - cage structure of saponins, cholesterol, phospholipids protein mixed with antigen
CpG- Cytosine + guanine separate by phosphate - these motifs bind to PRR (TLR-9) -> immune response
What are the indications for B cell replacement?
Primary antibody deficiencies
- X linked agammaglobinaemia
-X linked hyper IgM syndrome
Common variable immune deficiency
Secondary deficiencies
- haematological deficiency - CLL, Multiple myeloma
After BM transplant
What are some clinical examples of specific immunoglobulin replacement?
Hep B IgG
VZV IgG
Tetany IgG
Rabies IgG
What are the different types of adoptive T cell transfer?
Virus-specific
Tumour infiltrating (TIL)
T cell receptor (TCR)
Chimeric antigen receptor (CAR)
Explain the role of virus-specific T cell transfer in EBV
Used to prevent B cell lymphoproliferative disease in the immunosuppressed.
Blood sample from pt or donor.
-Isolate mononucleocytes
-Stim with EBV peptides
-Expansion of EBV specific T cells which can be reinfused into the patient
What are the differences between TCR and CAR T cell therapy
Both have T cells from pt removed and inserted vector (Viral or non-viral)
TCR - is just a specific T cell receptor eg against a tumour antigen
CAR T - is a recombinant receptor with T and B cell surface proteins so can activate both TCR (CD28 and CD23)and CD19
Explain the role of adjuvants and their MOA (Plus examples)
Increase immune response without altering vaccine specificity.
Mimic PAMOs action on TLR and PRRs
aluminium salts (humans), Lipids (monophosphoryl lipid A), oils (Freund’s adjuvant -animals), ISCOMS, CpG DNA
Explain TIL T cell therapy
Remove tumour from the patient
Stim T cells from the tumour with cytokines (IL-2) in the presence of tumour cells.
T cell undergo clonal expansion
reinsert into the patient - infiltrating lymphocytes
Where is CAR- T cell therapy being utilised
NH lymphoma and ALL
less effective in solid tumours
What is the mechanism of Ipilimumab?
Binds to CTLA4 (a TCR that recognises CD80 and CD86 APCs and transducers and inhibitory signal) thus preventing this inhibition and enhancing T cell response
What is the mechanism of Pembrolizumab and Nivolumab
Antibodies that bind the PD-ligand 1 and in turn upregulates T cell action.
PD-1 (prevents death) is present on APCs and tumour cells - its role is to inhibit T cells.
Give examples of cytokine therapies and their uses
INF -a: hairy cell leukaemia, CML, MM
INF-2a: Bechet’s disease
INF-y: Chronic granulomatous disease
IL-2: Renal cell cancer
What are the uses and complications of Ipilimumab (CTLA4 inhib T signalling) and Pembrolizumab and Nivolumab (PD-1 inhibs)?
Ipilimumab: used in Multiple myeloma
Pembrolizumab and Nivolumab: Multiple myeloma and advanced renal cancer
Complication- autoimmunity (RA, Thyroid, diabetes)
What are the different methods for suppressing the immune system?
Steroids Cytotoxic drugs Plasmapheresis Inhibiting cell signalling Agents targeting cell surface antigens Agents targeting cytokines
What is the action of corticosteroids on prostaglandins
Corticosteroids inhibit phospholipase A2 ( which is required for the conversion of Arachidonic acid to prostaglandins and leukotriens by COX
What is the action of corticosteroids on phagocytes
v phagocytosis,
v proteolytic enzyme release.
v phagocytes in inflamed tissue:
v chemoattractants, v expression of adhesion molecules on endothelium
What is the action of corticosteroids on lymphocytes
Lymphopenia (sequestered in lymphoid tissue CD4>CD8> b)
x cytokine expression
v Ab synth
^ apoptosis
What are the SEs of steroids
Metabolic- Diabetes, moo face, central adiposity, buffalo fat pat, dyslipidemia, osteoporosis, adrenal suppression, hirsutism, acne
Other- cataracts, glaucoma, peptic ulcers, pancreatitis, avascular necrosis, immunosuppression
What are cytotoxic drugs and give examples
Cyclophosphamide
Mycophenolate mofetil
azathioprine
What are the general side effects of cytotoxic drugs?
Bone marrow suppression - pancytopenia
loss of hair, sterility (M>F)
Infection risk - eg HSV and Pneumocystis jiroveci
What’s the MOA of cyclophosphamides
Alkylating agent of guanine -> DNA damage -> x cell replication.
(B>T>all high turnover cells)
What the indications for
a. cyclophosphamide
b. Mycophenolate mofetil
c. Azathioprine
a. major organ AI dissease eg SLE, GPA and anti-cancer
b. organ transplant (alt to azo), AI disease and vasculitis (alt to cylo)
c. Chron’s
What’s the MOA of mycophenolate mofetil?
Purine anti-metabolite-> prevents synthesis of guanosine -> prevents DNA replication (T>B cells)
What genetic varient should you check for before starting azathioprine
TPMT - thiopurine methyltransferase polymorphisms as they are unable to metabolism azathioprine 1:300.
susceptible to bm suppresion
Describe the process of plasmapheresis
The aim is to remove pathogenic antibodies from patient plasma.
Patient blood is passed through cells separator. Cellular constituents are reinfused. Plasma is treated to remove AB or plasma exchange - given albumin, re given to the patient
What are the indications of plasmapheresis
Severe AI disease.
- good pastures (anti-GMB)
-Severe acute MG (ANti-AChR)
Severe vascular rejection (HLA issues)`
Whats the MOA of Azothioprine
purine anti-metabolite/ analogue-> met to 6-mercaptopurine-> interferes with DNA synthesis (T>B)