Immunology Flashcards
What does a haemocytoblast differentiate into?
Common myeloid and common lymphoid progenitors.
What does a common myeloid progenitor differentiate into?
Mast cells, megakaryocyte, erythrocytes and myeloblast.
What do myeloblasts differentiate into?
Eosinophil, basophil, neutrophil and monocytes.
What do monocytes differentiate into?
Macrophages.
What do common lymphoid progenitors differentiate into?
Natural killer cells and lymphocytes.
What do lymphocytes differentiate into?
T cells and B cells.
What do B cells differentiate into?
Plasma cells which produce antibodies.
What is the function of the bone marrow?
Where all cells originate and where B cells mature.
What is the function of the thymus?
Where T cells mature and thymic tolerance.
What is the function of lymph nodes?
Where T and B cells accumulate.
What is the function of the spleen?
RBCs are recycled here.
What causes large, rubbery lymph nodes?
Lymphomas.
What is innate immunity?
Non-specific defence system you’re born with.
What are the features of innate immunity?
Non-specific, rapid, always active and no memory.
What part of the innate immune system usually kill pathogens?
Neutrophils, macrophages and the complement system.
What are the barriers involved in innate immunity?
Physical - skin, mucus, cilia.Chemical - lysozymes, stomach acid.
What is the complement system?
Part of innate immunity. Enhances the ability to destroy foreign antigens made up of plasma proteins that opsonise (tag) pathogens.
What are the pathways of the complement system?
C3 pathways - direct lysis, leukocyte attraction, coat invading organism.
Which six cells are involved in innate immunity?
Neutrophils, macrophages, eosinophils, basophils, mast cells and natural killer cells.
What are neutrophils and how many make up all WBCs?
Innate WBCs that make up 70% of WBCs.
What are macrophages? How long do they live for?
Innate WBCs involved in phagocytosis. Live for months to years.
What are eosinophils?
Innate WBC involved in parasitic infections.
What are basophils?
Circulating innate WBCs involved in allergy.
What are mast cells?
Innate WBCs that are fixed in tissues and involved in allergy and anaphylaxis.IgE binding - degranulation -> histamine. T1 hypersensitivity.
What are natural killer cells? Which pathogens do they kill and how?
Innate WBCs that kill virus infected cells. When activated they degranulate and release perforin (perforates viral infected cells).
How do innate immune cells recognise pathogens?
By TLRs. These are expressed in dendritic cells and macrophages.
What do TLRs respond to and why?
Pathogens and damage (PAMPs and DAMPs).-Activate immune response.
What are the types of TLRs? What does TLR5 recognise?
2-9.TLR5 - Flagella
What is the interface between innate and adaptive immunity?
The antigen-presenting cell (APC).
What is the function of the antigen-presenting cell?
They present foreign antigens to T helper cells which proliferates T helper cells and activates the B cells (humoral response).
What is adaptive immunity?
Acquired defence system to destroy and prevent the growth of pathogens (by usually antibodies).
What are the features of adaptive immunity?
Specific, slow, requires activation and has memory.
How does the adaptive immune system usually kill pathogens?
By antibodies.
Which cells are involved in adaptive immunity?
T and B lymphocytes.
Where do T cells mature?
In the thymus.
What are the types of T cell?
T helper cells, cytotoxic T cells and T memory cells.
What do T helper cells express and what does this do?
CD4 - Interact with MHC 2 and activates B cells and cytotoxic T cells.
What do cytotoxic T cells express and what does this do?
CD8 - Interact with MHC 1 and release perforin which lyses cells.
What are the two types of T helper cells and what do they do?
TH1 - Activate NK cells and macrophages (increased innate response).TH2 - Activates B cells to differentiate into plasma cells (increased adaptive response).
Where are B cells produced and matured?
In the bone marrow.
How are B cells activated and why is this important?
TH2 cells activated (APC and MHC2). TH2 cells release:IL4 - Induces B cell proliferation (clonal expansion)IL5 - Induces B cell differentiation into plasma cells.
What are antibodies and what do they do?
Molecules produced by differentiated plasma cells that neutralise toxins, opsonise pathogens and destroy pathogens.
What are the types of antibodies?
GAMED Ig’s (IgG, IgA, IgM, IgE, IgD).
Describe IgG (three things).
Most abundant Ig in blood. Key in secondary immune response. Can cross placenta.
Describe IgA. Where is to found? What shape does it form?
Most abundant Ig in total body. Found on mucosal linings and breast milk.Forms dimer.
Describe IgM. What does it activate? What shape do they form?
First Ig released in adaptive response.Activates the complement.Pentamer.
Describe IgE.
IgE activates mast cell and basophilic degranulation type 1 hypersensitivity (anaphylaxis).
Describe IgD.
Not important, function is not understood.
What are MHCs?
Major histocompatibility complexes (HLA molecules).
What is hypersensitivity?
Exaggerated or inappropriate immunological responses occurring in response to an antigen or allergen.
What are the types of hypersensitivity reactions?
Type 1 - Anaphylaxis - IgEType 2 - Antigen-antibody complexType 3 - Immune complex depositionType 4 - T-cell mediated
Explain the type 1 hypersensitivity reaction and give an example.
Anaphylaxis - IgE. IgE binds to basophilic mast cells, degranulates and releases histamine. E.g. atopy
Explain the type 2 hypersensitivity reaction and give an example.
IgG/IgM binds to antigen and activates complement at AA site binding. E.g. Goodpastures.
Explain type 3 hypersensitivity reaction and give an example.
IgG/IgA binds to antigen at site of AA deposition. E.g. SLE
Explain type 4 hypersensitivity reaction and give two examples.
TH1 activated by APCs - response. E.g. TB, MS.
What is anaphylaxis and its consequences?
Type 1 hypersensitivity - IgE. May present with anaphylactic shock (hypotension, tachycardia, pale, puffed).
What are the treatments for anaphylaxis?
ABCDE (airway, breathing, circulation, disability, exposure). Treat with 0.5mg IM adrenaline.
What is immunodeficiency?
When the immune system’s ability to fight disease and cancer is compromised or absent.
What are the types of immunodeficiency?
Acquired and inherited.Inherited - T cell defects, IgA deficiency.Acquired - HIV, chemotherapy.
What are the five features of immunodeficiency?
- Decreased CD4 in HIV.2. B cells may be deficient (less plasma cells, less antibodies).3. Neutrophil and macrophage deficiency.4. Complement deficiency.5. Hyposplenism.
What are vaccinations?
A form of artificial active immunity that trigger an immune response to mimic the natural infection without being symptomatic.
What types of vaccines are there? Give examples.
- Live attenuated - MMR2. Antigens3. Toxins - Tetanus4. Recombinant vaccines - Hep B5. mRNA - Covid-19 vaccines
What are the types of immunity?
Active (natural/artificial)Passive (natural/artificial)
Describe active immunity. Give examples of natural and artificial.
Ig production, secondary response, immunological memory.-Natural; Pathogens, produce memory cells.-Artificial; Vaccine mimics encountering pathogen and stimulates Ig production.
Describe passive immunity. Give an example of natural and artficial.
Ig’s passed to host, no memory, primary response.-Natural; Maternal Igs passed to baby in breast milk.-Artificial; Antivenom - injection of Ig’s from another organism.
What is immune tolerance?
A system to prevent faulty T/B cell response. Unresponsiveness of immune response to substances/tissues that would elicit an immune response.
What are the types of immune tolerance?
Central tolerance (thymic).Peripheral tolerance (lymph nodes).
What is autoimmunity?
A pathological response to self.
What are the types of autoimmunity?
Organ specific - T1DM (pancreas beta cells), MS (oligodendrocytes).Non-organ specific - RBCs (autoimmune haemolytic anaemia), rheumatoid arthritis.
What are cytokines?
Proteins secreted by immune and non-immune cells.
What are the five types of cytokines?
IFs, ILs, colony stimulating factors, TNFs, chemokines.
What is the function of interferons (IFN)?
They induce a state of antiviral resistance to uninfected cells.
What are the types of interferons (IFN) and what releases them?
IFN alpha and beta - Produced by virus infected cellsIFN gamma - Released by activated T cells
What is the function of interleukins (ILs)?
Cytokines that are either pro-inflammatory or anti-inflammatory.Can cause cells to divide, to differentiate and to secrete factors.
What does tumour necrosis factor do (TNF)?
Mediate inflammation and cytotoxic infections.
What is the function of chemokines?
Leukocyte chemoattractants.
Is the complement system continuously active?
No, has to be activated.
What is the C3b pathway in the complement system?
Opsonisation - Tag foreign pathogens to be eliminated by phagocytes.
What are the C3a and C5a pathways of the complement system?
Chemotaxes - Attracting phagocytes.
Which proteins are involved in direct lysis in the complement system?
MAC (membrane attack complex). C5b, C6, C7, C8, C9.
What are the three main function of specific antibodies?
- Neutralise toxins by binding.2. Increase opsonisation (phagocytosis after).3. Activate complement.
What shape is an IgM antibody?
Pentamer.
What shape is an IgA antibody?
Dimer.
Which cells are MHC 1 located on?
All cells.
Which cells are MHC II located on?
Only antigen presenting cells (APC).
How long do neutrophils live for?
Hours to days.
Which receptor do neutrophils express?
CD66.
What is a major function of neutrophils?
Mediating acute inflammation.
How do neutrophils kill pathogens?
By releasing ROS.
What are the types of macrophages?
Circulatory of resident (monocytes).
What are examples of resident monocytes?
Kupffer cells in liver.Alveolar macrophages in lungs.
What do macrophages clear?
Apoptotic debris.
What two things do macrophages have on their cell membrane?
TLRs and complement receptors.
How do basophils lead to hypersensitivity?
IgE binding → Degranulation → Histamine. T1 hypersensitivity.
Compare basophils and mast cells.
Both involved in allergy and hypersensitivity.Basophils circulated whereas mast cells are fixed in tissues.
Which cells mostly act as antigen-presenting cells?
Dendritic cells.
What are two other less common examples of antigen presenting cells?
Macrophages and B cells.
What is thymic tolerance and what are the two steps?
When T cells go to mature in the thymus.-Positive selection and negative selection.
What is positive selection is thymic tolerance?
The T cells are tested if they recognise MHCs (I and II).-If they do, they will be either CD4 or CD8 cells.-If they don’t they die by apoptosis.
What is negative selection in thymic tolerance?
To test if T cells bind to self-antigens and produce an immune response.-If they don’t they mature into CD4/CD8 cells.-If they bind, they die by apoptosis.
What is the function of MHCs?
To interact with T cells:-CD4 - Interact with MHCII on APCs.-CD8 - Interact with MHCI on all nucleated cells.
How are MHCs involved in autoimmune disease?
Mutations in them can give susceptibility to autoimmune diseases.-T1DM, coeliacs, SLE.
Which antibody mediates T1 hypersensitivity?
IgE.
Which antibodies mediate T2 hypersensitivity?
IgG, IgM.
Which antibodies mediate T3 hypersensitivty?
IgG, IgA.
What mediates T4 hypersensitivity?
T cells.
