Flashcards in Immune Response and Hypersensitivity Deck (98)
What are the 2 main subdivisions of the immune system?
Innate and adaptive.
What is innate immunity?
Non-specific defence mechanisms (e.g. skin, chemicals, immune cells).
What are the main subdivisions of the innate immune system? (3)
-Barrier and chemical mechanisms (e.g. skin)
-Pattern recognition receptor (PRR)
-Cellular (phagocytes, NK cells)
What is adaptive immunity?
Antigen-specific immune response.
What are the main subdivisions of the adaptive immune system? (2)
What is humoral immunity?
Immunity mediated by macromolecules ( not cells) found in ECF such as secreted antibodies and complement proteins.
What are the main components of the innate immune system? (5)
What are pattern recognition receptors (PRR)?
Antigen recognition receptors in the innate system.
Are PRRs identical?
No, there's a diversity of type, but each cell carries identical receptors of a given type.
What do PRRs commonly recognise? (2)
-Pathogen-associated molecular patterns (PAMPs)
-Danger associated molecular patterns (DAMPs)
What are the 2 groups of PRRs?
-Transmembrane (cell suraface) and intracellular
-Fluid-phase soluble molecules
Pattern recognition receptors:
What molecule does TLR4 recognise?
Pattern recognition receptors:
What molecule does TLR5 recognise?
Pattern recognition receptors:
What molecule does TLR9 (intracellular) recognise?
What are antimicrobial peptides (AMPs)?
Proteins produced in secretions >> break down proteins in microbes.
Give some examples of antimicrobial peptides.
Give some examples of cells that play a role in the innate immune system.
What are the complement components of the innate immune system?
-Classic and alternative complement pathway.
-Proteins that bind components
What are cytokines?
Molecules that mediate host defence and inflammation, and regulate the adaptive immune response.
What does autocrine mean?
Relating to a cell-produced substance that has an effect on the cell by which it is secreted.
What does paracrine mean?
Relating to a hormone which has effect only in the vicinity of the gland secreting it.
What does endocrine mean?
Relating to glands which secrete hormones or other products directly into the blood.
What is a fluid-phase recognition molecule?
-C-type lectin family
-Surfactant protein A / D
What is the function of fluid-phase recognition molecules? (3)
-Neutralisation of pathogens
-Recruitment of adaptive response
What do fluid-phase recognition molecules bind via?
Carbohydrate-recognition domains (CRDs).
How many carbohydrate-recognition domains does mannose-binding lectin have?
What are the main innate immune pathways? (3)
What is the role of IL1?
Initial cytokine >> unwell, muscle ache, etc.
What does IL1 target? (3)
When are TNF and IL6 produced?
What does TNF target? (4)
Adaptive immune response; what happens when a lymphocyte comes into contact with its specific antigen?
What happens in primary lymphoid organs?
Lymphocytes develop and mature.
What are the primary lymphoid organs? (2)
-Bone marrow (B cells)
-Thymus (T cells)
What happens in secondary lymphoid organs?
Initiate adaptive immune response and lymphocyte activation.
What are the secondary lymphoid organs? (3)
What is the range of antigenic variability?
How many genes does the human genome contain?
How is diversity increased in human antigen receptors?
What is the mechanism of antigen presentation?
Antigens are internalised
>> broken down into peptides
>> peptides associated with class 2 molecules
>> brought to cell surface
>> activate helper T cells
>> these produce cytokines
>> B cells, T cells, etc.
What are histocompatibility antigens?
Glycoproteins on mammalian cell surfaces.
-make us unique
Where were histocompatibility antigens first found?
-ABO blood groups on RBCs
What is another name for histocompatibility antigens?
Human leucocyte antigens (HLA).
-determine blood group
-used to match donors
How many classes of histocompatibility antigens are there?
Name the class 1 histocompatibility antigens. (3)
Name the class 2 histocompatibility antigens. (3)
What are MHC proteins?
Cell surface proteins that present antigenic peptides to T cells.
What type of T cell do MHC class 1 proteins present peptide to?
Cytotoxic T cells.
What type of T cell do MHC class 2 proteins present peptide to?
Helper T cells.
What is the function of B lymphocytes?
Produce and secrete antibodies.
What is the function of cytotoxic T lymphocytes?
Kills infected/damaged cells.
What is the function of helper T lymphocytes?
Secrete cytokines >> control immune response.
-help B and T lymphocytes
What is the function of suppressor T lymphocytes?
Dampen down the immune repsonse.
How does binding of antibodies to antigens inactivate them? (4)
-Agglutination of microbes
-Precipitation of antigens
(these 3 >> PHAGOCYTOSIS)
-Activation of complement system
What is agglutination?
Clumping of particles.
What protein secreted by cytotoxic T cells makes holes in the infected cell's membrane.
What is immunosuppression?
Reduced activation or efficacy of the immune system.
-can result in immunodeficiency
What is immunodeficiency?
Lack of an efficient immune system-susceptibility to infections.
What are the main uses of immunosupression? (3)
What is hypersensitivity?
Undesirable, sometime fatal, reactions produced by normal immune system against innocuous antigens in a pre-sensitised host.
What does innocuous mean?
What are the 4 types of hypersensitivity reactions?
I - IgE mediated
II - cytotoxic
III - immune complex
IV - cell mediated
What is another name for a severe type 1 (IgE mediated) reaction?
What is the general process of a type I hypersensitivity reaction?
IgE mediated mast cell and basophil degranulation
>> release of inflammatory mediators (e.g. histamine)
>> and synthesis of lipid mediators (e.g. leukotrienes)
What are the main clinical features of a Type I hypersensitivity reaction? (3)
-Fast onset (15-30 mins)
-Weal and flare
-Can have 2nd phase response
What are the common antigens associated with a Type I hypersensitivity reaction?
What common diseases are associated with Type I hypersensitivity reaction?
How is IgE produced?
By plasma cells under the control of IL-4 and CD40L-CD40 interaction.
How high are IgE serum levels?
-but high affinity receptor (FcR1) on mast cells and basophils
What are the 2 types of response associated with Type I hypersensitivity reactions?
-Early phase response
-Late phase response
What is the general process of the early phase response?
Mast cell activation (FcR1)
>> degranulation (release of pre-formed mediators) and synthesis of lipid mediators.
How are mast cells activated in Type I hypersensitivity reactions?
Cross-linking of FcR1 by allergen >> activation.
Name 3 common pre-formed mediators involved in Type I hypersensitivity reactions.
What is the main action of histamine? (2)
-Smooth muscle contraction
-Increased vascular permeability
What is the main action of kallikrein?
-similar actions to histamine
What lipid mediators are synthesised from arachidonic acid? (2)
-Prostaglandins (e.g. thromboxane)
What are the main cells involved in the late phase response? (3)
What is the role of basophils in the late phase response?
Similar to mast cells but over a longer time period.
-release of mediators
What is the role of eosinophils in the late phase response?
Attracted to sites of allergic inflammation by chemokines
>> release contents of granules (cytotoxic proteins)
>> tissue damage
What is the role of T cells in Type I hypersensitivity reactions?
Produce cytokines once activated.
-involved in both early and late phase responses
What is a major source of pathogenesis in allergic responses?
What type of reaction are Type II hypersensitivity reactions?
Antibody-mediated cytotoxic reactions.
What is the process of Type II hypersensitivity reactions?
Antibodies bind to antigen on cell membrane;
- activation of complement cascade >> cell lysis
- Aggregation of Fc portions >> opsonisation/phagocytosis/destruction
What are Type II hypersensitivity reactions initiated by? (2)
Which is more efficient; IgM or IgG?
Which requires multiple binding; IgM or IgG?
What sort of cells are normally affected by Type II hypersensitivity reactions?
What common disorders are associated with Type II hypersensitivity reactions?
-Blood group incompatibility
-Autoimmune haemolytic anaemias
-Affects neutrophils and platelets
What sort of reactions are Type III hypersensitivity reactions?
Immune complex reactions.
What is the general process of Type III hypersensitivity reactions?
Ig + Ab = AgAb complex
>> FcR bind C1q
>> complement activation
>> C5a attracts neutrophils
>> C3b opsonin
>> phagocytosis of complexes (enzymes released)
>> TISSUE DAMAGE.
What are the types of inactivation caused by antibody-mediated immunopathology? (3)
-DIRECT (e.g. B12 deficiency)
-INDIRECT (e.g. binding to hormones >> AgAb complex clearance)
What sort of reactions are Type IV hypersensitivity reactions?
T cell mediated reactions.
What is the general process of Type IV hypersensitivity reactions?
Initial perivascular infiltration of lymphocytes and monocytes
>> Langerhan's cells present antigen to T cells
>> T cells release cytokines
>> recruit macrophages
>> TISSUE DAMAGE
What do Type IV hypersensitivity reactions require?
Previous exposure to the antigen.
Give an example of a skin condition caused by T cell mediated cytotoxicity (Type IV).
-Nickel, poison ivy
>> DTH and cytotoxic reaction
What type of hypersensitivity reaction causes granulomatous reactions?
Type IV hypersensitivity reactions.
What are granulomas?
Collections of inflammatory cells (macrophages/lymphocytes) in tissues.
-IL2 release critical in initation of response