Immunology Flashcards
What is innate immunity?
An immune response that is present from birth
Give 3 features of an innate immune response
- ) Immediate
- ) Non-specific
- ) Slow
- ) No memory
What does PAMP stand for, and where is it found?
Pathogen associated molecular patterns, on microbe
What does PRR stand for, and where is it found?
Pattern recognition receptors, on cells
How is the innate immune system activated?
Activated by PRRs on dendritic cells recognising conserved PAMPs on microbes and triggering a response
What does TLR stand for?
Toll-like receptor
What does the complement system consist of?
Circulating inactive proteins synthesised by the liver that, when stimulated, trigger a proteolytic cascade
What do TLRs and other PRRs do?
Drive cytokine production
What 3 pathways is the complement system activated by?
- ) Classical
- ) Alternative
- ) Lectin
Which immune system is the complement system part of?
Innate
What are the 4 main steps of the classical pathway?
1) C1q binds to Fc domains of IgG/IgM or to pathogens, activating C1r and C1s
2) C1s cleave C4 to C4a and C4b
3) C4b binds to C2 forming C4b2b complex
4) C4b2b is a C3 convertase and cleaves C3
What is the alternative pathway activated by?
Bacterial cell wall
What is the classical pathway activated by?
An antibody
What are the 5 main steps of the alternative pathway?
1) C3 splits to form C3b and C3a
2) C3b forms a complex with factor B forming C3bB
3) Addition of factor B forms C3bBb
4) C3bBb is a C3 convertase, and catalyses the splitting of C3 (more C3b produced, positive feedback loop)
5) Rate of C3 conversion rises above rate of deactivation of convertase, pathway activates
What is the lectin pathway activated by?
Mannose binding lectin that is bound to a microbe
What are the 2 main steps of the lectin pathway?
1) MBL binds to mannose carbohydrate on surface of pathogen
2) Then same steps as classical
Give 3 things complement activation results in
- ) Increased vascular permeability
- ) Chemoattraction of leucocytes
- ) Enhanced phagocytosis
- ) Enhanced lysis (releases pro inflammatory markers)
What is the key step in the complement system, and why?
Cleavage of C3
C3b mediates opsonisation
What is opsonisation?
The labelling of targets for destruction by phagocytosis
Give the 7 steps of an inflammatory response
1) Bleeding stopped by coagulation
2) Acute inflammation by leukocyte recruitment
3) Killing pathogens, neutralising toxins, limiting pathogen spread
4) Clear pathogens/dead cells by phagocytosis
5) Proliferation of cells to repair the damage
6) Remove blood clot and remodel extracellular matrix
7) Re-establish normal structure/function
Give 3 polymorphonuclear leukocytes
- ) Neutrophil
- ) Eosinophil
- ) Basophil
What are neutrophils involved in?
Innate immunity and phagocytosis
What are eosinophils involved in?
Parasitic infections and allergic reactions
What are basophils involved in?
Parasitic infections and allergic reactions
Give 3 mononuclear leukocytes
- ) Monocyte
- ) T-cells
- ) B-cells
What are monocytes involved in? (4)
Innate and adaptive immunity, phagocytosis, Ag presentation
What do monocytes differentiate into?
Macrophages
What are T-cells involved in?
Adaptive immunity
What do T-cells differentiate into? (3)
T-regs, T-helpers, cytotoxic
What are B-cells involved in?
Adaptive immunity
What do B-cells differentiate into?
Plasma cells
Give 3 other cells of the immune system
- ) Mast cells
- ) Natural killer cells (NK)
- ) Dendritic cells
- ) Macrophages
What are mast cells involved in?
Parasitic infections and allergic reactions
What do mast cells release?
Histamine
Where are mast cells found?
Only in tissues
What do NK cells do?
Recognise and kill virus infected and tumour cells by apoptosis
What are macrophages involved in? (4)
Innate and adaptive immunity, phagocytosis, Ag presentation
What is an antibody?
A protein produced in respond to an antigen, can only bind to that specific antigen
What is an antigen?
A molecule that reacts with a preformed antibody and specific receptors on T cells
What is an epitope?
The part of the antigen that binds to the antibody/receptor binding site
What is affinity?
The measure of the binding strength between and epitope and an antibody binding site
Give 3 features of adaptive immunity
- ) Specific response
- ) Involves memory
- ) Cell mediated and humoral
- ) Quicker
What cells are against intracellular microbes?
T cells
What cells are against extracellular microbes?
B cells
What can T cells not recognise?
Antigens not bound to host cells
How is the processed antigen presented?
With MHC class II antigens on the APC surface
What does MHC stand for?
Major histocompatibility complex
What does APC stand for?
Antigen presenting cell
What is T cell selection?
T cells that recognise self are killed in the foetal thymus as they mature
What are MHC antigens?
Cell surface glycoproteins
What do class I MHCs present on?
All nucleated cells
What do class II MHCs present on? (4)
Dendritic cells, B lymphocytes, activated T cells, macrophages (APCs)
What do class III MHCs constituent of?
Early complement proteins C4 and C2
Where do T lymphocytes mature?
Thymus
What do cytotoxic CD8 T cells do?
Destroy infected intracellular cells
What do memory T cells do?
Survive after infection to respond rapidly to recurrent infections
What do helper T cells CD4 do? (3)
- ) Activate cytotoxic T cells
- ) Activate B cell antibody production
- ) Secrete cytokines
What do regulatory T cells do?
Negatively regulate immune response preventing autoimmunity, can suppress other T cell types
Give the 7 steps in which Th1 activation leads to stopping viral spread
1) APC presents an Ag with MHC II to a naive CD4 T cell
2) Stimulation with high levels of IL-12 activate naive cells to Th1 cells
3) Th1 cells go to secondary lymphoid tissue
4) Activated
5) Clonal expansion/proliferate
6) Th1 cells recognise Ag on infected cells
7) Th1 secretes INF gamma and stops virus spread
What type of cell is CD4?
Helper T cell
What type of cell is CD8?
Cytotoxic T cell
Where is the secondary lymphoid tissue?
Spleen, lymph nodes
When do B cells become activated?
When they have bound to their specific Ag
Where do activated B cells proliferate and differentiate?
Lymph nodes
What sort of antibodies/immunoglobulin do plasma cells secrete?
IgM
What is class switching?
IgM later turn into IgG, but have the same specificity
What are antibodies/immunoglobulins secreted by?
B lymphocytes
Where do B cells mature?
Bone marrow
What are the 5 main types of Ig?
- ) IgG
- ) IgM
- ) IgA
- ) IgD
- ) IgE
What is IgG involved in?
Important in secondary and memory response
Which Ig can cross the placenta?
IgG
What shape is IgG?
Y shaped
What is IgM involved in?
Important in primary response, pentamer
Where is IgG mainly found?
Serum and tissues
Where is IgM mainly found?
Blood
What does IgA do?
Protects mucosal surfaces
What is predominant in mucous secretions?
Secretory IgA
What Ig is present as an antigen specific receptor on B cells?
Monomeric form mIgM
Where is IgA mainly found?
Serum and secretions
What does IgD do?
May have a role in respiratory infection
What Ig is present on mature B cells?
Transmembrane monomeric form mIgD
What is IgE involved in?
Allergic and parasitic reactions
What 2 types of inflammatory cell have a high affinity for IgE?
Basophils and mast cells
Give 3 functions of an antibody
- ) Opsonisation
- ) Activation of complements
- ) Antibody dependent cell mediated cytotoxicity
What is the Fab region of an antibody?
Variable, binds specifically to antigens
What is the Fc region of an antibody?
Constant, bind to Fc receptors on cells such as phagocytes and complement proteins
What are cytokines?
Proteins secreted by immune and non-immune cells
What are the 4 main types of cytokines?
- ) Inferferons
- ) Interleukins
- ) Colony stimulating factors
- ) Tumour necrosis factors
What do interferons do?
Induce a state of antiviral resistance in uninfected cells and limit the spread of viral infection
What can interleukins be?
Pro or anti-inflammatory
What do interleukins do?
Cause cells to divide, differentiate or secrete factors
What do colony stimulating factors involved in?
Directing the diversion and differentiation of bone marrow stem cells
What are colony stimulating factors the precursors of?
Leukocytes
What do tumour necrosis factors do?
Mediate inflammation and cytotoxic reaction
What are chemokines?
Chemotaxic cytokines
What do chemokines do?
Direct the movement of leukocytes and other cells from the blood stream into tissues or lymph organs by binding to specific receptors on cells
What is autoimmunity?
A system of immune responses of an organism against its own cells and tissues
Give 2 causes of autoimmune disease
- ) Tissue damage
- ) Disturbed functions from autoimmunity
What does organ specific autoimmune disease usually affect?
Endocrine glands
Give 2 environmental triggers for autoimmune diseases
- ) Hormones
- ) Infection
- ) Drugs
- ) UV radiation
What is the recognition and elimination of cancer cells mediated by? (2)
T cells and NK cells
What is cancer immunosurveillance?
The system that can recognise and destroy new cells
What is cancer immunoediting?
When changes in the immunogenicity of tumours due to the anti-tumour response of the immune results in immune resistant variants
What are over expressed on cancer cells?
Tumour associated antigens
Where are tumour associated antigens found?
Normal and tumour cells
Where are tumour specific antigens found?
Tumour cells
How can tumours change immune responses?
By promoting immune suppressor cells, so they can be seen as self
What are transplants crossmatched to detect?
Anti HLA antibodies
What does HLA stand for?
Human leukocyte antigen
What is the HLA complex?
A gene complex encoding the MHC proteins in humans
What immunological cell plays a central role in rejection of a transplant?
CD4 T helper cells recognise the donor MHC and recruit effector cells
Give 2 ways in which we can prevent transplant rejection
- ) Tissue typing
- ) Cross matching
- ) Immunosuppression
What is an allergy?
An abnormal response to harmful foreign material, usually involving IgE
Give 3 clinical indications for an allergy
- ) Eczema
- ) Itching
- ) Mucous
- ) Airway constriction
- ) Anaphylaxis
- ) Vomiting
- ) Diarrhoea
Give 3 cells that are involved in an allergic response
- ) Mast cells
- ) Eosinophils
- ) Lymphocytes
- ) Macrophages
- ) Cytokines
What are the 4 main types of hypersensitivity reactions?
Type I - allergic and immediate Type II - cytotoxic, antibody to cell bound antigen Type III - immune complex Type IV - delayed type ACID
What Ig does type I hypersensitivity involve?
IgE
EGGT
What Ig does type II hypersensitivity involve?
IgG
EGGT
What Ig does type III hypersensitivity involve?
IgG
EGGT
What cell does type IV hypersensitivity involve?
T cells
EGGT
Give an example of a type I hypersensitivity reaction
Peanut allergy, latex, bee venom, antibiotics
How does type I hypersensitivity occur?
Binding of antigen by IgE on mast cells/basophils releases preformed mediators
Give an example of a type II hypersensitivity reaction
Drugs, haemolytic anaemia
How does type II hypersensitivity occur?
Cell destruction caused by activation of complement system and promotion of phagocytosis, body’s own cells attacked
Give an example of a type III hypersensitivity reaction
RA, glomerulonephritis, Goodpasture’s
How does type III hypersensitivity occur?
Deposition of IgG containing immune complexes, especially in joints and kidneys
Give an example of a type IV hypersensitivity reaction
DM, MS, Crohn’s, contact dermatitis
How does type IV hypersensitivity occur?
Local inflammation occurs after days, granulation tissues delay response
What does immunodeficiency present as?
Serious persistent, unusual or recurrent infections
How do we treat immunodeficiency?
Bone marrow transplant
Give 3 causes of immunodeficiency
- ) Antibody deficiency
- ) Cellular immunity deficient
- ) Phagocytic/complement defects
- ) Genetic (primary)
What does C3b go on to form?
Membrane attack complex