Immunology Flashcards
what is another good way to learn immunology ?
use the quizzes linked to the lectures
describe origin of B cells and maturation stages
- originate in bone marrow or lymph nodes
- become activated when antigen (from T cell / antigen presenting cell) binds to receptor
- B memory cells retain the and keep comminucating with T cells for more help
- B plasma cells remove membrane anchor and secrete immunoglobulins
- cytokines from the T cell determine type of Ig IgA, IgE, IgM, IgG
describe structure of antibody
Y shaped structure
four polypeptides : 2 heavy chains, 2 light chains
tips of the Y variable specific to antigen
what are the primary immune organs and what do they make
Thymus : T cells
Bone marrow : B cells
development and maturation of immune cells
describe action of T 1 helper cells
recognise MHC II complexes on macrophages and help macrophages digest pathogens
describe action TH 2 cells
recognise MHC II / antigen complexes on beta cells and help them to become plasma cells to secrete antibodies
describe action cytotoxic T cells
recognise MHC I / Ag complexes on virus infected cells and kill them via release of perforins and granzymes
name some secondary immune tissues
adenoids, peyers patches , mucosa associated lymph tissue ( MALT ), appendix, spleen, lymph nodes
what are the features of the innate immune system and give some examples
fast response, non specific, no memory
epithelial barriers, dendritic cells, mast cells, phagocytes, complement, NK cells
what are the features of the adaptive immune system and give examples
slower ( days ) , specific and have memory
T cells and B cells ( produce abs )
what cell is the precursor to macrophages
monocytes
macrophages have specific types in different tissues - name some
bone - osteoclasts
lung : alveolar macrophage
brain : microglial cells
liver : kupffer cells
name cells involved in the innate immune system ( there are 6 )
Natural Killer Cells
neutrophils - have enzymes to excrete
macrophages - phagocytose and present ags to T cells
dendritic cells - phagocytose and present ags to T cells
mast cells
eosinophils
how do macrophages and dendritic cells recognise pathogens
DAMPS ( damage ), PAMPS ( pathogen ) and MAMPS ( microbe ) associated protein structure
by Toll like receptors
What is the term used to describe a rounded aggregate of activated macrophages/giant cells?
A granuloma
what is the complement pathway ?
30 proteins which can destroy bacteria within seconds, eg lectin responds to microbial sugars, can respond to lipids from bacteria ( fast )
classical pathway activated by antibodies ( if met before ie memory )
What is the function of lysosomes?
- Lysosomes are membrane-bound organelles that contain enzymes capable of breaking down (digesting) proteins, nucleic acids, carbohydrates and lipids
- destroy pathogens
In cell membranes, phosphotidylserine normally faces inwards. What happens if this molecule flips to face outwards?
It becomes an ‘eat me’ signal for phagocytes (a cell which can gobble other cells or particles), in the setting of apoptosis (programmed cell death).
How specific is the immediate response to a pathogen?
The immediate response activates the innate immune system and therefore has limited specificity.
What is the main cytokine produced by sentinel cells when they are activated by DAMPs and PAMPs?
Interleukin 1 (IL-1).
Name the 3 complement system activation pathways and explain how they are activated.
- Classical pathway. Activated by antigen binding to IgG or IgM which activates C1.
- Alternative pathway. Activated by microbial components directly.
- Mannose-binding lectin pathway. Activated by mannose-binding lectin binding to mannose on the surface of a bacterium.
What is the Complement System?
A system of pro-inflammatory proteins produced by the liver which circulate as inactive precursors until they are activated by 1 of 3 pathways.
List 4 consequences of complement system activation.
- Formation of anaphylatoxins (C3a, C4a + C5a) which cause histamine to be released from mast cells. C5a is a chemotactic + activation agent for neutrophils, monocytes, eosinophils and basophils.
- Opsonisation. C3b is the main opsonin (an ‘eat-me’ signal for neutrophils and macrophages which have C3b receptors).
- Cell lysis. The final stage of the complement cascade results in the formation of a membrane attack complex (C5b, C6, C7, C8 and C9) flooding the cell with water and ions and causing lysis.
- Immunoglobulin clearance. Removal of immune complexes from the circulation
Describe the consequences of mast cell activation
- Mast cells contain pre-formed histamine granules which can be quickly released causing blood vessels to dilate and to leak.
- Mast cells also cause a delayed response by producing leukotrienes.
What is produced when 5-lipooxygnease acts on Arachidonic acid?
Leukotrienes
List 4 effects of prostaglandin production in the context of acute inflammation
- Vasodilation.
- Increased vascular permeability.
- Pain (PGE2).
- Fever (PGE2).
List 4 consequences of leukotriene production in the context of acute inflammation
- Vasoconstriction.
- Bronchospasm.
- Increased vascular permeability.
- Attraction and activation of neutrophils (LTB4).
What are the 3 main functions of bradykinin?
- Vasodilation.
- Increased vascular permeability.
- Pain.
What are Toll-like receptors?
- These are receptors that present on macrophages and dendritic cells which can be activated by PAMPs.
- TLR activates immune response genes producing cytokines.
- TLRs are also present on cells of adaptive immunity (lymphocytes).
describe steps in phagocytosis ( 6 )
- activation of phagocytic cell / chemotaxis
- recognition of invading microbes ( PAMPs )
- ingestion and form phagosomes
- fusion with lysosome ( phagolysome )
- microbe killing and form residual bodies
- elimination of digested contents ( exocytosis )
( a diagram would be nice )
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where are immune cells made?
- within bone marrow during haematopoiesis
where do lymphocytes mature and receive their immunological ‘education’ before being released into the bloodstream?
- thymus gland
once lymphocytes mature in the thymus gland, where do they migrate to?
- lymph nodes
other than lymph nodes, what 2 other organs play a role in the immune system?
- spleen (massive lymph node): site of antigen presentation
- liver: contains its own cohort of phagocytes and lymphocytes, it also synthesises acute phase proteins such as CRP in response to infection
what are some physical and chemical barrier mechanisms in humans to prevent the invasion of infective organisms?
- intrinsic epithelial barriers exist between the body and outside world: epithelial cell walls have tight junctions between them and are hard to penetrate (eg. lining of mouth, lungs)
- the continuous longitudinal flow of air or fluid through most body systems: creates a flushing action which prevents bacteria from adhering to structures
- movement of mucus by cilia in lungs: prevents bacteria from adhering to structures
- desquamation of skin and epithelial cells: prevents adherence of microorganisms
- natural acids in parts of the body: eg. lysozymes in saliva, hydrochloric acid in stomach
- natural antibacterial peptides on the skin and surface linings of lungs and gut (eg. defensins, chemokines)
- normal bacterial flora colonise parts of body: compete with infective microorganisms (eg. vaginal lactobacilli produce lactate- creates acidic environment and destroys infective organisms)
what cells are granulocytes?
- neutrophils: first line of defence against all infections
- eosinophils: involved in IgE mediated allergic disorders such as asthma
- basophils (or mast cells): have a role in type 1 hypersensitivity reactions through their binding with IgE antibodies
what do macrophages derive from?
- blood monocytes
what are the main roles of tissue macrophages?
- they ‘tidy up’ any pathogens, foreign debris, and any old/dead cells using phagocytosis
- they also perform antigen presentation and can activate memory cells
describe the process by which a tissue macrophage would destroy a pathogen/foreign piece of debris/old or dead cell
- tissue macrophages have processes on their cell membranes called pseudopodia which extend around the unlucky item they’re about to eat
- once internalised, the engulfed material is contained within a phagosome
- the phagosome then fuses with a lysosome which contains either reactive oxygen species or enzymes which break down its contents
give an example of a macrophage found in bone
- osteoclasts
what is the role of dendritic cells?
- once formed in bone marrow they circulate in the bloodstream until they reach their target tissues, where they are activated by pathogens and differentiate into their mature forms
- they phagocytose pathogens before migrating to lymph nodes, where they present antigens on their cell surfaces with the costimulatory molecules required to activate the adaptive immune response
- they have numerous dendritic processes
what cells are lymphocytes?
- B cells
- T cells
- Natural killer cells
what are the 2 types of B cells?
- plasma cells (mature B cells) that secrete antibodies
- memory B cells
- B cells surface markers include CD19, CD20, CD21, MHC II
what are the 4 types of T cell?
- helper T cells (CD4): facilitate the activation of the immune response and stimulate effector cells
- cytotoxic T cells (CD8): also known as killer T cells or effector T cells, provide cell-mediated immunity
- regulatory T cells (CD25+FOXP3): also known as suppressor T cells, provide role of limiting the immune response to prevent excessive damage to tissues and organs
- memory T cells (CD62+CCR7): remember what happened to allow immune system to mount a faster and more effective response if the infective organism enters body again
what are natural killer cells also known as, what do they express, and what is their role?
- also known as large granular lymphocytes
- they express CD16, CD56, and CD8
- NK cells form part of both the innate and adaptive immune systems and are able to destroy pathogens without the need to prior activation by specific antigens
what are the 4 main parts of the immune response?
- the innate immune system
- the acute inflammatory response
- antigen presentation
4a. humoral immunity
4b. cell-mediated immunity
what are the key features of the innate immune response? (not cellular level)
- very fast
- non-specific
- no memory
what does the innate immune response consist of?
- innate cellular response
- innate chemical response
describe the innate cellular response
PHAGOCYTES (eg. dendritic cells, tissue macrophages, neutrophils):
- phagocytes identify pathogens by recognising pathogen-associated molecular patterns (PAMPs) using pathogen recognition receptors (PRRs)
- (toll-like receptors (TLRs) are an example of a PRR)
- phagocytes identify, internalise, kill, and digest pathogens into their component proteins
- phagocytes then present the digested protein antigens to the cells of the adaptive immune system via major histocompatibility complexes (MHCs)
