Immunology Flashcards
What is innate immunity?
Instinctive, non-specific, doesn’t depend on lymphocytes, present from birth
What is adaptive immunity?
Specific acquired/learned immunity, requires lymphocytes, antibodies
What forms haematocrit?
Erythrocytes and platelets
What is serum?
Plasma without fibrinogen and other clotting factors
What are the groups of leukocytes?
- Lymphocytes
- Phagocytes
- Auxiliary cells
What cells are phagocytes?
- Mononuclear phagocyte
- Neutrophil
- Eosinophil
What cells are auxiliary cells?
- Basophil
- Mast cell
- Platelets
What do leukocytes derive from?
Multipotent haematopoietic stemm cells
What are the dendritic cells in the liver and skin?
Liver - Kupffer
Skin - Langerhans
What are the modes of action of complement C?
- Direct lysis
- Attract more leukocytes to site of infection
- Coat invading organisms
What are the 5 classes of immunoglobulins?
IgA, IgG, IgM, IgD, IgE
What does the Fc region bind?
Receptors on leukocytes
What does the Fab region bind?
Bind to different specific antigens
What is the most prominent Ig?
IgG
How many binding sites does IgG have?
2
How many binding sites does IgM have?
10
Where is IgM found?
Blood
What is IgA the prominent Ig in?
Mucous secretions
What cells express an IgE specific receptor?
Basophils and mast cells
What is released when basophils and mast cells bind an antigen?
Histamine
What are cytokines?
Proteins secreted by immune and non-immune cells
What is the function of interferons?
To induce a state of antiviral resistance in uninfected cells and limit spread of viral infection
What releases IFNa+B?
Virus infected cells
What releases IFNy?
Activated Th1 cells
What have a switch to turn off the immune response?
Interleukins
What is the function of interleukins?
To cause cells to divide, differentiate and to secrete factors
What is the function of colony stimulating factors?
To direct division and differentiation on bone marrow stem cells
What is the function of tumour necrosis factors?
Mediate inflammation and cytotoxic reactions
What are chemokine?
Group of proteins that direct movement of leukocytes from bloodstream into tissues or lymph organs by binding to specific receptors on cells
What is innate immunity composed of?
- Physical and chemical barriers
- Phagocytic cells
- Blood proteins
What are the steps of the inflammatory response?
- Coagulation
- Acute inflammation
- Kill pathogens, neutralise toxins, limit pathogen spread
- Phagocytosis
- Proliferation of cells to repair damage
- Remove blood clot
- Re-establish normal function of tissue
What is inflammation?
A series of reactions the brings cells and molecules of immune system to sites of infection or damage
What are the hallmarks of inflammation?
- Increased blood supply
- Increased vascular permeability
- Increased leukocyte trans endothelial migration extravasation
What is acute inflammation?
Complete elimination of a pathogen followed by resolution of damage, disappearance of leukocytes and full regeneration of tissue
What is chronic inflammation?
Persistent, unresolved inflammation
What do pattern recognition receptors bind?
Pathogen associated molecular patterns (PAMPs)
What are the functions of complement?
- Lysis
- Chemotaxis
- Opsonisation
What are the activation pathways for C’?
- Classical
- Alternative
- Lectin
What is the function of TNFa released by macrophages in extravasation?
Activates endothelium to make it sticky and secretes chemokines
What happens following chemokine secretion in extravasation?
Chemokine sticky to endothelium surface and cause neutrophil to stop on surface
What happens once the neutrophil is bound to the surface in extravasation?
It squeezes through endothelial cell gaps and moves to the site of infection
What are the steps of phagocytosis?
- Binding
- Engulfment
- Phagosome formation
- Phagolysosome
- Membrane disruption/fusion
- Phagocytes internalise and kill invading organisms
What are the 2 killing pathways in neutrophils and macrophages?
- O2 dependent
2. O2 independent
Describe adaptive immunity
- Antigen specificity and diversity
- Immunological memory
- Specific self/non-self recognition
Why does cell-mediated immunity require cell to cell contact?
- To control Ab responses via contact with B cells
2. To directly recognise and kill viral infected cells
Where are T cells killed in T cell selection?
Foetal thymus
How do T cells recognise antigens?
- MHC molecule presents peptide
- Antigen peptide bound to MHC molecule
- TCR recognises MHC and peptide
What codes for MHC in humans?
Human leukocyte antigen genes
Where are Class I MHC found?
All cells
Where are Class II MHC found?
Antigen presenting cells
What is the function of CTL?
Forms proteolytic granules, releases perforins and granulysin, induces apoptosis
What Ig are expressed on B cells?
IgM and IgD
How do B cells present antigens to T cells?
Via MHC II
What happens when Th2 bind to B cells?
They secrete cytokines
What happens when cytokines are released?
They cause B cells to divide - clonal expansion
What do B cells differentiate into after clonal expansion?
Plasma cells and memory B cells
What Ig do plasma cells tend to secrete?
IgM
What is it called when IgM change to IgG?
Class switching
How do antibodies work?
- Neutralise toxins by binding to it
- Increase opsonisation
- Activate complement
What rate of vaccination uptake is needed for herd immunity to work?
95%
What is the pathway in antibody production?
Antigen -> B lymphocytes -> plasma cells -> soluble Ab
What class of glycoprotein do antibodies belong to?
Immunoglobulins
What part of the antibody is responsible for antigen recognition?
Fab region - variable in sequence
What part of the antibody is responsible for antigen elimination?
Fc region - constant in sequence
What are the 2 chains that make up constant regions and their size?
Light chain - 25kD
Heavy chain - 50kD
What encodes variable and constant regions?
Exons
What are the 5 classes of immunoglobulin?
IgG, IgM, IgA, IgD, IgE
What is the main Ab class in serum and tissues?
IgG
What response types are IgG important for?
Secondary/memory responses
What response type are IgM important for?
Primary responses
What Ab type protects mucosal surfaces?
IgA
Which Ab type are involved in allergic reactions?
IgE
What are the 2 types of light chain?
Kappa and lambda
How can Ab protect against infection?
- Specific binding/ multivalency (Fab)
2. Enhance innate mechanisms (Fc)
How do Fab regions protect against infection?
- Neutralise
- Immobilise motile microbes
- Prevent binding to, and infection of host cells
- Form complexes
How do Fc regions protect against infection?
- Activate complement
2. Bind Fc receptors
What are the Fc receptors and what do they do?
- Phagocytes - enhance phagocytosis
- Mast cells - release inflammatory mediators
- NK cells - enhanced killing of infected cells
What controls behaviour of leukocytes?
Cytokines