Immunology Flashcards
What are cytokines?
Proteins secreted by immune and non-immune cells
What are the different types of cytokines?
- Interferons
- Interleukins
- Colony stimulating factors
- Tumour necrosis factors
- chemokines
What is the role of interferons?
Induce a state of antiviral resistance in unaffected cells limiting the spread of infection
What is the role of interleukins?
Cause cells to divide, differentiate and secrete factors. Can be pro or anti-inflammatory.
What is the role of colony stimulating factors?
Stimulate growth and differentiation of immature leukocytes in bone marrow
What is the role of tumour necrosis factors?
Mediate a pro-inflammatory response in cytotoxic reactions
What are chemokines and what do they do?
Direct leukocyte movement, certain chemokines attract certain white blood cells.
What is innate immunity?
- Rapid
- non-specific
- doesn’t depend on lymphocytes
- present from birth
What is adaptive immunity?
- specific
- learned
- requires lymphocytes and antibodies
What are clinical indications of allergy?
- Skin: swelling, itching, redness
- Airways: mucus, bronchoconstriction
- GI: bloating, vomiting
- Anaphylaxis: airways, breathing, circulation
What is allergy?
abnormal response to harmless foreign material (antigens)
What is the pathogenesis of allergy?
- involves IgE, IgG4 and IgA
- genetic factors
- mast cells, eosinophils, basophils
What is hypersensitivity?
- overreaction of the immune system to an antigen which would not normally trigger a response
What is type 1 hypersensitivity?
- occurs on second exposure to antigen/drug
- IgE antibodies formed after exposure to molecule
- IgE becomes attached to mast cells/leucocytes, expressed as cell surface receptor
What happens upon re-exposure to an allergen?
- mast cell degranulation
- release of histamine, prostaglandins, leukotrienes, platelet activating factor
What are the symptoms of anaphylaxis?
- occurs with in minutes, lasts 1-2 hrs
- vasodilation
- inc vascular permeability
- bronchoconstriction
- urticaria
- angio-oedema
- 1-20% have biphasic response
What common diseases have vaccines?
- diphtheria
- mumps
- tetanus
- poliomyelitis
- smallpox
What are the 4 types of hypersensitivity reactions?
I: Immediate: IgE antibodies
II: cytotoxic: IgG/IgM antibodies
III: Immune complex: IgG/IgM: IgM is released mainly in the primary response and IgG is released thereafter
IV: Delayed: T lymphocyte mediated
What is ABCDE in anaphylaxis?
airway, breathing, circulation, disability, exposure
What does IgG do?
- most abundant
- present on mature B cells and in serum
- only antibody that can cross placenta and gives passive immunity
What does IgM do?
- found on the surface of and secreted by B cells
- 1st type produced in foetal development and against new infection
What does IgA do?
- most prevalent in secretions like saliva and mucus
- resistant to enzymatic digestion and act as neutralising antibodies
- forms barriers at mucosal surfaces preventing pathogenic invasion
What does IgE do?
- Mainly found on mast cells
- associated with type 1 hypersensitivity
- triggers histamine release from mast cells and basophils
- part of response to parasitic infection
What does IgD do?
- present on surface of B cells
- has a role in B cell and antibody production
What are major histocompatibility proteins?
- important in graft regeneration
- very polymorphic
- major role in initiating T cell responses
What is the role of MHC 1?
- expressed by all nucleated cells
- displays antigen to CD8 positive (cytotoxic) T cells
What is the role of MHC 2?
- expressed by macrophages, dendritic cells, B cells
- display antigen to CD4 positive (helper) T cells
What is the process of T cell antigen recognition?
- viral proteins broken down in cytosol and transported to ER
- Bind to MHC1 and are presented on the cell surface
- Activated cytotoxic T cells induce apoptosis
- Helper T cell recognises peptide bound to MHC2
- Peptides bind to MHC2 in endosomes and are presented
- B cells induced
What is the complement cascade and what are the 3 modes of action?
- serum proteins secreted by the liver and activated as part of the immune response
- direct lysis: membrane attack complex formation
- opsonisation: inc phagocytosis
- inflammation: macrophage chemotaxis
What are the 3 modes of action of the complement cascade?
- direct lysis
- attract more leukocytes to site of infection
- coat invading organism
How do T cells recognise antigens in association with MHCs?
- MHC molecule presents peptide
- antigen peptide bound to MHC molecule
- T cell receptor recognises MHC and peptide
What can secreted antibody do?
- neutralise toxin by binding to it
- increase opsonisation > phagocytosis
- activate complement
What are pathogen associated molecular patterns?
- substances unique to pathogens
- dsRNA
What are TLRs?
- pattern recognition receptors on cells of the innate immune system that allow them to recognise PAMPs
What is the role of natural killer (NK) cells?
Release lytic granules that kill virus infected cells
What are some features of active immunity?
- produced by host immune system
- durable, effective protection
- effective after lag period
- immunological memory
- negative phase
What are some features of passive immunity?
- pooled antibodies transferred into host
- transient (lasts short time) and less effective
- no lag period or memory
- no negative phase
What is immunodeficiency?
- the failure of the immune system to protect the body from infection
- due to a defect in immune function or a deficiency in a component of the immune system
What is autoimmunity?
- a breakdown of immune tolerance
- this is the unresponsiveness of the immune system to self antigens
How do B cells mature?
- arise from common lymphoid progenitor in bone marrow
- selection processes
- migrate from BM to lymphoid follicles in spleen and areas of lymphoid activation and defence
What is positive selection in B cells?
- only functional receptors develop further
- B cells successfully bind to its ligand and induce survival signals
What is negative selection in B cells?
- B cells respond to self antigens in BM
- undergo receptor editing, anergy, apoptosis
- reduces risk of autoimmune reactions
Where are B cells commonly found?
- Peyer’s patches of colon
- mucosa-associated lymphoid tissue (MALT)
- BALT (bronchial)
- mucosal linings
What type of PAMPs do these TLRs identify and which pathogens are they found on:
- TLR 2
- TLR 4
- TLR 5
- TLR 9?
- TLR2: peptidoglycans on gram +ve bacteria
- TLR 4: lipopolysaccharide on gram -ve bacteria
- TLR 5: flagellin on bacteria
- TLR 9: dsDNA on viruses
What do the cytokines interferon α and β do?
- released by T cells, B cells, macrophages
- inhibit viral replication
What are monocytes?
- phagocytes found in the bloodstream
- differentiate into macrophages
- kidney bean shaped nucleus
What are macrophages?
- derived from monocytes, found in tissues
- phagocytose cellular debris
- antigen presenting, induce inflammation, recruit cells
- e.g. microglia, Kupffer cells
What are neutrophils?
- most abundant WBC
- phagocytic, 1st in acute inflammation
- release cytokines and induce inflammation
What is a basophil?
- Mature into mast cells
- Express surface IgE and release histamine
- Role in allergies and immunity
- prevent coagulation and agglutination
- NON phagocytic
What is an eosinophil?
- phagocytic
- neutralise histamine and restrict inflammatory response
- antagonist to basophils
- present in parasitic infection
