Immunology Flashcards
1
Q
what are the main types of host defence
A
- intrinsic - always present and can be physical or chemical
- innate - induced by an infection e.g. interferon, cytokines, macrophages etc.
- adaptive - is tailored to a specific pathogen – T and B cells.
2
Q
what is the difference between innate and adaptive immunity
A
innate you are born with and adaptive you acquire
3
Q
what are the 2 main effectors in innate immunity
A
- specialist macrophages [kupffer cells, dendritic cells, alveolar macrophages]
- neutrophils
4
Q
what are the precursor of alveolar macrophages
A
monocytes
5
Q
what are neutrophils
A
a type of WBC
6
Q
where are neutrophils made
A
in the bone marrow, making the myeloid cells.
7
Q
what is a key component of neutrophils that helps with their function
A
- They contain granules:
- PRIMARY – myeloperoxidase, elastase, cathepsins, defensins
- SECONDARY – receptors, lysozyme, collagenase
8
Q
neutrophils are not involved in inflammation - T/F
A
False
- neutrophils participate in the inflammatory response and protect against infection
- They are present in blood at all times but are only activated when needed → generation of ROS
- as the insult is removed and healing begins, the inflamm cells must be removed via
- exudate
- migration
- apoptosis
9
Q
what are the 7 functions of neutrophils
A
- identification of pathogen
- activation
- adhesion
- chemotaxis / migration
- phagocytosis
- bacterial killing -
- achieved via enzymes and ROS generation by NADPH oxidase complex
- apoptosis
10
Q
which cells mediate adaptive immunity and by what mechanism?
A
- B cells by humoral responses
- T cells by cell-mediated responses
11
Q
what is an antigen
A
- a molecule able to induce a specific immune response from the host.
- Can be proteins, polysaccharides, lipids, DNA etc.
12
Q
what is an epitope
A
One antigen can have different epitopes – recognisable regions of the antigen
13
Q
what are the 4 main types of T-cells
A
- Cytotoxic T-cells
- T-helper cells
- T-regulatory cells
- Memory T- cells
14
Q
where are B and T cells made and where do they mature?
A
- B cells:
- made in the bone marrow
- maturation begins in the bone marrow and ends in the spleen, lymph nodes
- T cells
- made in the bone marrow
- Mature in the thymus
15
Q
what are 3 key functions of adaptive immunity?
A
- specificity and diversity
- self- tolerance - recognition of self-antigens and elimination of autoreactive clones
- memory via signature BCRs and TCRs.
16
Q
In what form do T and B cells recognise antigens?
A
- B cells
- B cell receptors recognise antigens in the native form AND when presented by antigen presenting cells.
- T cells recognise antigens presented on MHCs on APCs
- APCs include: dendritic cells, macrophages, B cells
17
Q
what is an antibody
A
a protein with a constant and a variable region
18
Q
describe cell-mediated immunity
A
t-cells can have CD4 or CD 8 expression
- CD8
- a cell that is infected presents the pathogen’s antigen on its surface via an MHC1 molecule
- T-cells that fit the antigen, with CD8 expression, encounter and bind to MHC1 presenting cells
- all nucleated cells have MHC1
- this → activation of the T-cell → CD8 cytotoxic T-cell response.
- CD4
- an antigen presenting cell encounters a pathogen and presents the antigen on its surface via MHC2
- the APC travels to the lymph node and presents to a matching T-helper cell with CD4 expression
- this binding → activation and multiplication of the T-cells
- T-helper cells and CD4 cytotoxic T-cells are produced
- the helper cells
- help B cells produce antibodies
- form memory T-cells
- form Regulatory T-cells to stop immun overreaction and help identify self-antigens
- the helper cells
19
Q
Describe Humoral immunity
A
- the pathogen’s antigen binds to a matching BCR either in its native state or via and APC.
- the antigen is then taken up into the B cell by endocytosis and the antigen is presented on its surface via MHC2
- a follicular T-helper cell with a matching TCR binds to the antigen presented on MHC2 on the B-cell → activation of the follicular T-cell → production of helper factors
- helper factors activate the B-cell → plasma cell formation and memory B-cell formation.
20
Q
how are such variable BCRs and TCRs created
A
- VDJ gene recombination
- Variable, Diversity, Joining segments
- this recombination process is very random → ⇡ diversity.
21
Q
what is somatic hypermutation and where does is occur?
A
- after a matching BCR binds to an antigen it proliferates.
- during proliferation loads of mutations occur in the binding regions of the BCR to increase affinity for the antigen → more efficient antibodies.
- only occurs in B cells
22
Q
what is immune tolerance and how is it mediated?
A
- immune tolerance is the bodies ability to not respond to the adaptive immunity system to avoid an overreaction.
- T-reg cells are responsible for this by killing immune cells with receptors capable of binding to self-cells.
23
Q
how many hypersensitivity classes are there?
A
4
- Type 1: Allergy, anaphylaxis and atopy – IgE dependent acute response
- IgG binding to self antigens (autoimmune)
- immune complex diseases
- delayed type hypersensitivity reaction
24
Q
describe a type 1 hypersensitivity response
A
- Type 1: Allergy, anaphylaxis and atopy – IgE dependent acute response
- involved in conditions such as asthma, eczema and hay fever
- IgE causes release of histamine from mast cells by activating FcεR1 receptor. → vasodilation and opening up of gap junctions
- treated with antihistamines, steroids and avoiding triggers
- effects seen immediately - within an hour
25
describe a type 2 hypersensitivity response
**IgG binding to self antigens (autoimmune)**
* cytotoxic
* the immune system attack the body's own cells
* e.g.
* effect seen in hours - days
26
Describe a type 3 hypersensitivity response
**Immune complex disease**
* A large scale immune response
* complexes of IgG precipitate and can't be cleared by macrophages
* e.g. Farmers lung
* effects seen within 7-10 days
27
describe a type 4 hypersensitivity response
**delayed hypersensitivity reaction**
* Type IV hypersensitivity is a T-cell-mediated hypersensitivity, meaning the inflammation and potential tissue damage is caused by either T helper cells (CD4+) or cytotoxic T cells (CD8+).
* antibodies are not involved
* e.g. tuberculosis
* effects seen in day - weeks - months
28
characteristics of IgG
* most abundant antibody/ immunoglobulin
* acts as an opsonin - binds to the pathogen and signals phagocytes towards it for phagocytosis
29
characteristics of IgA
* found on the mucosa surface
* prevents pathogens from entering the body
30
characteristics of IgE
* involved in type 1 hypersensitivity reactions
* seen in asthma, atopic dermatitis and hayfever
31
characteristics of IgM
* **IgM** is the first antibody secreted by the adaptive immune system
* it activates complement
* doesnt require t-cell help
32
characteristics of IgM
* **IgM** is the first antibody secreted by the adaptive immune system
* it activates complement
* doesnt require t-cell help
33
Characteristics of IgD
* helps mature B cells leave the bone marrow
