Immunology Flashcards
What is the main function of the immune system?
Protects against infectious agents
What are the two main systems of immunity?
Innate immunity
Adaptive immunity
What form of immunity acts as a first line of defence? E.g. barriers, cells, soluble factors
Innate immunity
What are key features of the innate immunity?
-present at birth
-responds rapidly
- has no specificity
- has no memory
What are some physical barriers in innate immunity?
Skin, epithelial cell layer, mucosa, cilia, bronchi
what are some chemical barriers in innate immunity?
-acidity in stomach
- alkaline secretions
-lysozyme in tears
What is the main form of biological barrier in innate immunity?
Competition with commensal organisms
What are examples of cells in innate immunity?
-phagocytes
-natural killer cells
-eosinophils
What cells are phagocytic in nature?
- monocytes
- macrophages
- neutrophils
What is the role of NK cells?
To kill tumour cells and virally infected cells
What is the role of eosinophils?
Attack and kill parasites
What are examples of soluble factors?
- lysozymes
- complement
- cytokines
- acute phase proteins
What is the role of lysozymes?
Protects against bacteria, viruses and fungi
What are cytokines?
Proteins that are part of the natural defences
The innate and adaptive immune systems cooperate with one another. True or false?
True
What are the two components of adaptive immunity?
humoral and cellular
What are key features of adaptive immunity?
-slow to start
-adaptive
- highly specific
-memory
-recognition of self and non-self
What does humoral immunity involve?
Antibodies (immunoglobulins)
What produces immunoglobulins?
B lymphocytes
What does cellular immunity involve?
Lymphocytes
What are the two types of lymphocytes
B and T lymphocytes
What are the two types of T cell?
Helper T cells
Cytotoxic T cells
What is the role of helper T cells?
Help B cells produce antibodies, in turn aiding humoral immunity
What is the role of cytotoxic T cells?
Destroy infected target cells with specific antigens, and spare uninfected cells.
What are effector functions?
Part of humoral response, they form an essential link between innate and adaptive immunity.
What are the two main roles of the immune system?
Recognition function
Effector function
What is recognition function?
Identifies a substance or antigen as foreign
What is an antigen?
Any substance which elicits an immune response
What part of an antigen is recognised by antibodies (humoral) and T cells ( cellular)?
The epitope/antigenic determinant
What is the KEY point to remember about antigens?
They are foreign
What are the two main roles of the cells of the immune system?
- Migrate into tissues to detect foreign antigens
- Accumulate in specialised organs to develop and differentiate
Name the five types of white blood cells
- monocytes
- eosinophils
- basophils
- lymphocytes
- neutrophils
What are the two different lineages of white blood cells?
- lymphoid lineage
- myeloid lineage
What cells are associated with the lymphoid lineage of white blood cells?
Lymphocytes
What cells are associated with the myeloid lineage of white blood cells?
Granulocytes and monocytes
Neutrophils, eosinophils and basophils are all types of what cell?
Granulocytes
What cell makes up 95% of circulating granulocytes?
Neutrophils
What cell is 10-20 micro metres in diameter?
Neutrophils
What type of nucleus do neutrophils have?
Multi-lobed
How do neutrophils enter tissues?
They adhere to endothelial cells and squeeze between them to leave the circulation and enter tissues
What is the main role of neutrophils?
Phagocytosis
What type of nucleus to eosinophils have?
Bi-lobed nucleus
The cells which releases toxin-containing granules upon activation in order to kill large pathogens (parasites), are known as?
Eosinophils
Which white blood cell is least present in the circulation?
Basophils
What is the difference between basophils and mast cells?
Mast cells are ONLY found in tissues, not the bloodstream.
What type of nucleus does a monocytes have?
Horse-shoe shaped
What are important features of monocytes?
Pinochet if vesicles and lysosomal granules
What do the lysosomes in monocytes contain?
Peroxidase and acid hydrolases
What is the main function if macrophages?
Phagocytosis
Name four types of accessory cell
- platelets
- antigen presenting cells (APC)
- mast cells
- endothelial cells
What role is associated with platelets
Blood clotting and inflammation
What role is associated with antigen presenting cells (APC)?
They present antigens to T cells and produce cytokines
What is the function of endothelial cells?
They control lymphocyte “traffic” and “distribution”
What is the role of mast cells?
To release histamine (usually in an allergic reaction)
Lymphocytes are involved in both cellular and humoral immunity. True or false?
True
Where are lymphocytes found?
In blood, lymph and specialised tissue
Where do lymphocytes originate?
In bone marrow from pluripotent cells
Where are B cells produced?
Bone marrow
Where are T cells produced?
Thymus
What are monoclonal antibodies used for?
As cell markers, they are highly specific and used to study cell surfaces
When does activation of lymphocytes occur?
Only on binding of antigen by antigen receptor
Where are antibodies (immunoglobulins) produced?
Plasma cells ( activated B cells)
What is clonal expansion a result of?
Binding of antigen to lymphocyte receptor
What does clonal expansion produce?
More activated and memory cells
A more rapid and effective response of lymphocytes to foreign antigens is a result of?
Clonal expansion
Tissues where immune response occurs are usually rich in what?
Macrophages
What is required for an immune response to occur?
Cooperation of cells, cell to cell contact and secretion of cytokines
What is another word for immunoglobulin?
Antibody
What are activated B cells called?
Plasma cells
What are the five classes of immunoglobulins ( IgG)?
IgG
IgM
IgA
IgD
IgE
What shape do immunoglobulins have?
Y shape
What are three important regions on an immunoglobulin?
Fab region
Fc region
Hinge
What are the two chains of immunoglobulin structure?
Heavy chain and light chain
What is the “hinge” region of the immunoglobulin?
Disulphide bridge
What is the recognition function of antibodies?
The Fab arms bind to antigens
What is the effector function of antibodies?
Interaction of Fc region on antibody with effector molecules (this is a clearance mechanism to get rid of foreign bodies)
What are the two types of light chains on antibodies?
- Lambda
- Kappa
What two globular domains will light chains on antibodies fold up into?
VL and CL
What determines the class of antibody?
Heavy chains
How many domains will heavy chains on antibodies fold up into and what are they?
4 (or 5) domains
VH,CH1,CH2,CH3 (and CH4)
What are found in V domains?
Complementary determining regions (CDR’s)
What are key in determining which antigen will bind?
Complementary determining regions (CDR’s)
What forms the antigen binding site?
Complementary determining regions (CDR’s)
Where are antigen binding sites found on immunoglobulins?
At the tip of the Fab arms
What type of immunoglobulin is most abundant in plasma?
IgG
How many subclasses does IgG have and what are they?
4 subclasses
IgG1, IgG2, IgG3, IgG4
What is the role of IgG
Triggers complement and phagocytosis
What immunoglobulin class is the only one to cross the placenta from mother to foetus?
IgG
What antibody is only in plasma and secretions, not tissues and why?
IgM, its too large to enter tissues
What immunoglobulin is predominant in the secondary antibody response?
IgG
What immunoglobulin has a special feature known as a ‘J joining chain’ ?
IgM
What is the shape and number of binding sites of IgM?
Five Y-shaped units with 10 binding sites (FAB arms) for antigen
What is the function of IgM?
Activates complement
Which antibody is predominant in the first antibody response?
IgM
What antibody is largely associated with seromucous secretions ( e.g. saliva)?
IgA
What are the two subclassses of IgA?
IgA1 and IgA2
What is IgE’s effector function?
It interacts with high affinity receptor: Fc£R1
Where is the high affinity receptor, Fc£RI expressed?
On mast cells and basophils (it is associated with the allergic response)
Which immunoglobulin is important against parasitic infections?
IgE
What immunoglobulin is found on the surface of lymphocytes?
IgD
Which region of an antibody is recognition associated with?
Fab arms
Which region of an antibody is effector function associated with?
Fc region
Define complement
A system of plasma proteins, protects the host from infection through a cascade of reactions that occurs on the surface of pathogens, recruiting and enhancing phagocytosis and leading to Lysis of cells.
Where precursors trigger proteolytic enzymes to go on and trigger other precursors. What is this known as?
Enzyme cascade
What are the three pathways involved in complement?
- classical
- Lectin
- alternative
Deficiency in what inhibitor will result in recurrent bacterial infections?
C3 inhibitor
Which of the three complement pathways is the first major line of defence against systemic infection?
Alternative pathway
Define lysis
Break down of cell
Define opsonisation
Attracts phagocytosis
What is released from mast cells in responses to anaphylaxis?
Histamine
What is the function of chemotaxis?
Causes phagocytes to migrate to infection site
What inhibitor deficiency will cause inappropriate activation of complement system?
C1 inhibitor
What can deficiencies in the classical complement pathway be associated with?
Autoimmune disorders
What is the specificity of lymphocytes achieved by?
Antigen receptors on cell surface
What is the antigen receptor on B cells?
Cell-surface antibody
What is the antigen receptor of T cells?
T cell receptor (TCR)
What do B cells synthesise and secrete?
Immunoglobulins
How do B cells produce immunoglobulins?
They are activated by binding antigens, then they differentiate into plasma cells which actively produce immunoglobulins
What is the initial immunoglobulin produced by B cells?
IgM
What immunoglobulins are produced by memory B cells?
IgG, IgA and IgE
What immunoglobulin do T cell independent antigens produce In small amounts?
IgM
What is a T cell receptor (TCR)?
A structure on T cell surface that recognises antigen
What are the two classes of T cells?
- helper T cell ( Th)
- cytotoxic T cell ( Tc)
What important cell surface protein do helper T cells express?
CD4
What important cell surface protein do cytotoxic T cells present?
CD8
What are the cell surface proteins, CD4 and CD8, required for?
For an effective response to antigen
What is the role of antigen presenting cells ( APC)?
Phagocytose foreign bodies
What do helper T cells secrete after binding to antigen? And what is their importance?
Cytokines, which control immune response
What are the two main functions of cytokines in controlling immune response?
- favour macrophage activation and cell mediated responses
- stimulate B cells to produce antibodies
An exaggerated, inappropriate adaptive immune response is known as?
Hypersensitivity
What can be the result of hypersensitivity?
Inflammatory reactions and tissue damage
When does hypersensitivity manifest, on the first contact or second contact?
Second contact
How many classifications of hypersensitivity are there?
4
Which hypersensitivity classifications are antibody mediated?
Class I, II and III
Which type of hypersensitivity classification is mediated by T cells and macrophages?
Class IV
Describe type I hypersensitivity
IgE response to non-harmful environmental antigens
What high affinity receptor on mast cells does IgE bind to?
Fc£R1
What does the second encounter to an antigen trigger?
The release of inflammatory mediators such as histamine
What are severe type I hypersensitivity reactions with systemic symptoms known as?
Anaphylactic shock
What chemical must be sued to treat anaphylaxis?
Adrenaline
Which class of hypersensitivity is antibody- dependent cytotoxic?
Type II
Does type II hypersensitivity occur slower or faster than type I?
Slower ( within 18-24hrs)
What classification of hypersensitivity is mediated by the persistence and deposition of antibody-antigen immune complexes?
Type III
What does deposition of immune complexes cause?
Inflammation
What class of hypersensitivity is delayed, occurring within 48-72 hrs post antigen exposure?
Type IV
What are the three types of type IV hypersensitivity?
- Contact
- Tuberculin
- Granulomatous
What are the two phases of type IV hypersensitivity?
- Sensitisation
- Elicitation (inflammation)
What class of hypersensitivity can sometimes be seen as a reaction to dental materials e.g. amalgam, gold, mercury and resin-based materials?
Type IV
What is the most key step of adaptive immunity?
Lymphocytes must recognise antigen
Which cells only recognise parts of antigens expressed on cell surfaces?
T cells
What are major histocompatibility complex (MHC) molecules also referred to as?
Human leukocyte antigens (HLA)
What are the two MHC families?
Class I and Class II
What are the three members of the Class I MHC family?
HLA-A, HLA-B, HLA-C
What are the three members of the Class II MHC family?
HLA-DP, HLA-DQ, HLA-DR
What MHC class is expressed on all nucleated cells?
Class I
Which MHC class is expressed only on leukocytes which present antigen T cells? e.g. monocytes
Class II
What are the three clinical implications of MHC?
- Tissue grafting
- Certain HLA types exposed to certain disease
- Forensic medicine
Which MHC class has a structure where the peptide-binding cleft is more open?
Class I
What do MHC molecules present to cells?
Antigenic peptides
what type of T cell does MHC class I present peptides to?
Cytotoxic T cell
what type of T cell does MHC class II present peptides to?
Helper T cell
Define the breakdown of self-tolerant mechanisms in the immune system
Autoimmunity
What antibodies develop in autoimmunity and what do they recognise?
Auto reactive antibodies that recognise self antigens
What are the two classes of autoimmune disease?
Organ-specific and Non organ-specific
what reactions can organ-specific autoimmunity bring about?
Type II hypersensitivity and cell mediated reactions
Define the chronic autoimmune disease of mucosal membranes and/or skin
Cicatrical Pemphigoid
What are oral indicators of Sjogren’s disease?
- oral candida
- dental caries
- dry lips
- dry and lobulated tongue
