General Flashcards
What is Apostasis?
Removing cells that have died of natural causes
When does Apostasis normally occur?
Embryonic development and ageing
What is the main overall purpose of Apostasis?
Maintain cell populations within tissues.
What is adaptive immunity and what allows it to be adaptive?
It is specific due to the presence of T&B lymphocytes
What is innate immunity?
Non-specific - natural immune system
What type of immunity does the skin cause and how does it do this?
Innate immunity. Protects underlying tissues from microbes.
What is the technical name for sweat glands and what are their purpose?
Sudoriferous (sweat) hands produce lysosomes that degrade peptidoglycands.
What are peptidoglycands composed of and what are their purpose?
Essential component of a bacterial cell wall - prevents the bacterial cell from bursting due to turgor pressure.
Mesh-like macromolecule composed of glycan chains and short peptides.
What is the Stratum Corneum and what is its purpose?
Outer layer or flat, dead cells on the skin which are filled with keratin and provide a physics barrier to invasion, abrasion and dehydration.
Name a type of non-pathogenic bacteria that surpasses virulent bacteria.
Commensal bacteria. Non-pathogenic bacteria.
Where is commensal bacteria found - examples.
Skin, mouth, reproductive regions, gastrointestinal tracts.
How do commensal bacteria act as a form of innate immunity?
They attach to the skin therefore blocking areas where pathogenic bacteria can attach. They also compete with pathogenic for nutrients so less nutrients are available on the skin for pathogenic bacteria. They also release antibacterial substances such as colicins.
What antibacterial substances do commensal bacteria release?
Colicins-proteins, short fatty acids.
How do mucus membranes act as a form of innate immunity?
How is mucus able to be a form of immunity.
Tracts lines with mucus membranes trap and protect us against microbes. Mucus is a long branched carbohydrate and is therefore viscous and able to trap foreign bodies for phagocytosis.
How do hairs in the nose act as a type of innate immunity?
Increase surface area and therefore increase trapping potential.
Name types of innate immunity (general).
Mucous membranes, hairs, acid, flushing, commensal bacteria, skin, eyes, ears, mouth.
What is secreted from the ears as part of innate immunity?
Cerumen waxy secretion from the sebaceous glands.
What is produced by a humoural immune response?
Antibodies
What is produced by a cell-mediated immune response?
Cytotoxic T lymphocytes.
Where does Hematopoiesis occur?
The hematopoietic system (bone marrow, liver, spleen etc.)
When does Hematopoiesis begin?
Embryonic development.
What (in general) is hematopoiesis?
Replacing old red blood cells with new red blood cells.
Name the 2 main categories of phagocytic cells
Granulocytes and Macrophages
Name 2 types of granulocytes and any further details.
Neutrophils- Highly active, short life span. Monocytes- Travel round the body, develop into macrophages.
Name two types of macrophages and any further details.
Wandering macrophages- travel as monocytes around the body, do chemotaxis during inflammation.
Fixed Macrophages- Present in most organs.
What are the 2 ways that a phagocyte attaches to a bacterium?
Antibody is made that attaches to the bacterium. A receptor present on the phagocyte then attaches to the antibody and they bind.
OR
A complement molecule attaches to the bacterium and then to a complement receptor on the phagosome.
What is a Phagolysosome?
A digestive vesicle formed within a cell by the fusion of a phagaosome containing ingested material and a lysosome containing hydrolytic enzymes.
What are the 2 killing mechanisms of Phagoytosis?
Oxygen-dependent and Oxygen-independent
What happens during oxygen-dependent killing mechanisms of phagocytosis?
Lysosomes degrade bacterial cell walls, cationic proteins cause pH to fall, defensives bind to bacterial membranes and form pores, acid hydrolase enzymes degrade carbohydrates.
What are the 3 ways that Apoptosis can occur?
Intrinsic pathway
Extrinsic pathway
Apoptosis Inducing Factor
Describe the intrinsic apoptosis pathway.
Cell damaged- BAX released- Inhibits release of BCL2 from mitochondria membrane. BAX punctures holes in outer mitochondrial membrane. Cytohrome C released into cytoplasm and causes apoptosome to form. Activates Caspase 9. Kills organelles.
Describe the extrinsic apoptosis pathway.
Death receptors (integral membrane proteins) bind to death activating molecules outside the cell. Caspase 8 activated inside cell. Destroys organelles.
How does the Apoptosis inducing factor theory work?
AIF is transferred into the cytoplasm of the cell and then into the nucleus, binding to the genetic material if a cell is damages.
Destroys DNA
Where is apoptosis inducing factor found ?
Intermembrane space between the inner and outer mitochondrial membranes.
How do macrophages generally work in terms of B cells?
Macrophages engulf and break down different types of pathogens. They then present the antigens from the pathogen on their own membrane. Complimentary B lymphocytes bind to the antigen receptor sites and cell mediated immunity will occur. This cell mediated immunity activates helper T cells to differentiate into plasma and memory B cells. Allows many antibodies to be formed that are complimentary to the initial antigen on the pathogen.
Where are B lymphocytes produced?
Bone marrow
Where can an example of humoural immunity be found?
In Macrophages.
Where are T lymphocytes produced and matured?
Produced- Bone marrow
Matured- Thymus
What happens to T-lymphocytes when the body is infected and how does cell mediated immunity then occur?
T-lymphocutes differentiate into helper T cells and cytotoxic T cells. The cytotoxic T cells travel to the site of infection and use antibodies on their surface to bind to antigens on the pathogens surface. Then then release perforin proteins which kill the pathogen cells. T memory cells are also formed as well as suppressor cells that can regulate the immune response.
Where does Hematopoeisis occur?
Bone marrow
What type of cells to Haematopoeitic stem cells differentiate into?
Myeloid cell types or Lymphoid cell types.
What types of Lymphoid cells are present in Haematopoeisis?
T lymphocytes and B lymphocytes
Name a type of Myeloid cell
Erythrocyte, Megakaryocyte, Monocyte, Neutrophil, Basophil, Eosinophil.
What type of cell is a Megakaryocyte and what is its function?
Myeloid cell - gives off cytoplasm to form platelets.
Describe the naming difference in T and B cells before and after they have matured.
Immature- B Lymphoblasts and T Lymphoblasts.
Mature - B Lymphocytes and T Lymphocytes.
What are dendritic cells and where are they found?
A type of immune cell found in the sin, gut, lungs, digestive tract etc.
Explain in general how an enzyme- cascade system works and what it is.
An in-active enzyme is activated. This newly activated enzyme then activates another enzyme and the cycle continues.
The initial effect is amplified.
What are 4 major cascade systems in the blood?
Blood clotting
Kinin
Firbrinolytic
Complement
Draw a flow diagram showing how the alternative complement system causes immunity based on C3.
IN NOTES !!!
What are the 3 general outcomes of the alternative complement pathway.
Cytolysis, phagocytosis, inflammation.
Give an example Opsonisation and its benefits.
C3b receptors on the macrophages and C3b proteins on the phagocyte are complimentary and therefore bind. This aids the phagocytosis process.
Benefits = drastically reduces the % of the phagocyte present in the organism as compared with normal phagocytosis.
Where are most complement enzymes before activation?
In the blood as pre-enzymes.
What is the general onset time and duration of chronic inflammation?
Slow onset, long duration
What is the general onset time and duration of acute inflammation?
Rapid onset, short duration
What are the 3 pathways of the complement system?
Alternative, Classical, Lectin
What usually causes acute inflammation ?
Microbes, chemical irritants, physical trauma, exposure to extreme temperature.
What cell type is used to combat acute inflammation ?
Neutrophils
Where are neutrophils activated during the acute inflammation process?
In the endothelium cells lining blood vessels.
What are the features of activated neutrophils in the acute inflammation system?
Increased receptors for chemoattractants, prostaglandins , leukotrienes and FCs. As well as more complement proteins.
How does activation of neutrophils affect metabolic activity and hows this helpful for immunity.
Neutrophils stimulate metabolic activity which produces oxygen and nitrogen containing intermediates such as hydrogen peroxide which are harmful chemical mediators used to kill the pathogens.
Outline to sequence of events in acute inflammation.
Pathogen enter tissue and cause damage.
Mast cells come into. contact with the pathogen and release histamine, prostaglandins and leukotrienes.
Histamine causes violation of arterioles, increasing blood flow.
Capillar permeability increases, causing oedema.
Complement proteins leave the capillary and are activated by the phagocyte.
Chemotaxis of neutrophils to the affected area.
Killing of pathogen by neutrophils - phagocyte.
Tissue repair
How are prostaglandins and Leukotrienes stored ?
They cannot be stored so must be made from scratch during the acute inflammation process.
What is oedema?
The osmotic balance between the blood and tissue in question is damaged. Molecules such as plasma proteins are able to move through membranes and causes swelling of the tissue.
What tissue damage can occur due to acute inflammation?
Tissue damage can occur but is usually very minor and impermanent.
What systems are in place to limit the tissue damage during acute inflammation?
Chemicals such as TGF beta stop and slow the inflammatory response.
What repairs are made after acute inflammation damage?
Fibroblasts are stimulated to repair the extra-cellular matrix for cells and produce collagen to repair tissue.
What are the symptoms of the inflammation (Latin name and explanation ).
Calor - heat Dolor - Pain Rubor - Redness Tumour - Swelling Functio Laesa - loss of function
What is extravasation in general terms?
How neutrophils move from the blood vessels to the site of damage.
What is the purpose of the vascular endothelium in cells?
Acts as a gateway regulating movement of molecules between cells and the blood.
What type of molecules are vital for Extravasation?
Cell adhesion molecules (CAMs).
Explain the process of Extravasation and how it allows neutrophils to reach the invaded site.
The mucin molecules on neutrophils and the E-selectin molecules on the endothelial cell bind - low affinity binding. This causes the endothelial cell to release Chemokine. Chemokine activates integrin and therefore allows a firm bonding between the neutrophil and endothelial cell using CAMS. The neutrophils can then migrate to the affected area as hey are attracted by chemoattractants.
What are interferons (general)?
Proteins produced by certain types of cells infected with viruses.
What is the main function of interferons and are they specific?
Non-specific
Interferons inhibit viral replication.
What are the functions of type 1 interferons and what are the type 1 interferons?
Alpha and beta interferons. Suppress tumours and metastasis.
Used to trat Kaposi’s sarcoma, genital warts and hepatitis C.
What is metastasis?
Abit of tumour splits off and goes to another part of the body to use a secondary tumour.
What are the type 2 interferons and what are their functions?
Gamma interferons.
Activates neutrophil and macrophages to enhance phagocytosis and the inflammatory process.
What cell types are the 2 interferons secreted from?
Natural killer cells and cytotoxic T cells.
How do interferons work to inhibit viral replication?
Interferons diffuse into neighbouring cells and bind to surface receptors. Interferons stimulate tissue cells to synthesise anti-viral proteins that inhibit viral replication.
By what method do natural killer cells kill cells?
Cytolysis and they also induce apoptosis.
What cells differentiate into natural killer cells?
Common lymphoid progenitor cells - innate lymphoid cells - natural killer cells.
Where are natural killer cells found?
Lymph nodes, spleen, bone marrow, blood.
Why are natural killer cells so fast acting and powerful?
They produce and respond to the stimulus to create a magnifying effect.
How do natural killer cells cause cytolysis?
They secrete perforin. Perforin forms holes in the plasma membranes of cells. Plasma proteins can therefore move into and out of the cell and change the osmotic gradient. A Lot of water moves into the cell by osmosis and causes osmotic lysis.
What types of cell are defensives active against?
Bacteria, fungi and some viruses.
How do defensives kill off pathogens?
They form pores in target cells and therefore affect osmotic potential - leading to osmotic lysis.
What are cells are pattern recognition receptors on and what pattern types do they recognise?
Proteins on innate immune cells and epithelial cells.
They recognise pathogen-associated molecular patterns and damage-associated molecular patterns.
What is the purpose of patter recognition receptors in the inflammatory process?
These proteins bind to pathogens and release inflammatory cytokines.
What response accompanies the acute phase response?
The local inflammatory response.
What happens during the acute phase response?
Rapid rise in the levels of acute phase serum proteins. These proteins limit the release of and toxidity of bacteria They bind to bacterial phospholipids, activate complement proteins and therefore enhance phagocytosis.
What stimulates the release the release of acute phase serum proteins?
Cytokines and macrophages.
Where are acute phase serum proteins made?
The liver
What is the purpose/ function of acute phase serum proteins?
They limit the release and toxicity of bacteria by binding to bacterial phospholipids, activating complementing bacteria and therefore enhancing phagocytosis.
What are the effects of the acute phase response ?
Increased body temperature (not ideal for pathogens), ACTH (hormone released which causes cytosol to be made and activate the white blood cells).
Where is ACTH hormone made and released?
Made = pituitary gland Released = adrenal glands
What is the effects of ACTH being released into the adrenal glands?
Activates which blood cells.
What are the 2 mechanisms for specific immunity?
Humoral immunity
Cell mediated immunity
What does the specificity of humoral immunity rely on?
Antibodies
What does the specificity of cell mediated immunity rely on?
T cells
Define antigen .
Any substance that when introduced to the body, is recognised as foreign and is capable of inducing a specific immune response .
Define immunogenicity .
The ability to induce an immune response .
What is produced when a B cell comes into contact with an immunogen?
Effector B lymphocytes and Memory B cells .
What is produced when T cells come into contact with an immunogen?
Effector T lymphocytes and T memory cells are produced .
Is an immunogen always an antigen?
Yes
Is an antigen always an immunogen?
No
What factors is immuogenicity determined by?
Degree of foreigness, molecular size, chemical composition and heterogeneity, susceptibility to antigen processing and presentation .
How does degree of foreigness affect immunogenicity?
The more foreign the microbe is and the less similar it is to body cells, the more likely to trigger an immune response .
How does phylogenetic evolution affect immunogenicity of a microbe?
As phylogenetic distance increases, the more likely the foreign body is to cause an immune response as it appears less like a self component .
Why do some self-components trigger an auto immune response?
Some self-components are sequestered (hidden) so may be recognised as foreign if they enter other regions of the body .
How does molecular size affect immunogenicity?
The larger the immunogen, the larger the immune response .
How do aromatic amino acids affect immunogenicity?
Increase immunogenicity .
What type of stereo-isomers are non-immunogenic?
D isomers because they cannot be degraded .
How does solubility increase immunogenicity?
The more insoluble a microbe, the more it aids phagocytosis and therefore the more it aids immunogenicity .
What varies the effects of the immunogen on an individual
The genotype of the recipient, immunogen dosage, imunogen route, adjuvants .
What are adjuvants in terms of immunogens ?
They work with the immunogen to enhance receptors .
Define Atnigenicity .
The ability to combine with products of the immune response .
What are endogenous antigens and what cells are they recognised by?
Recognised by Cytotoxic T cells .
Originate inside the body and presents antigens on its surface .
What are exogenous antigens?
Originate outside the body and are recognised by T helper cells .
Give an example of an exogenous microbe .
Bacterial infections .
What receptors do B lymphocytes have to recognise antigens?
Have B cell antibodies on their surface which act as antigen receptors .
What receptors do T lymphocytes have on their surface to recognise antigens?
T cell antigen receptors .
What is the advantage of having large antigens?
The larger the antigen the larger the binding site for T/B lymphocytes .
Which polysaccharides do/ don’t trigger an immune response?
Small dont
Large do
What are epitopes?
The site on an antigen molecule where the antibody binds .
How many epitopes sites can an antibody bind to?
1 - they are highly specific .
How many epitopes do antigens have on their surface and why?
Many because this allows the effective production of many different antibody types to allow an effective immune response .
What are haptens?
Molcules which are too small to initiate an immune response .
How can haptens be made to cause an immune response?
Haptens can be linked to carrier molecules to trigger an immune response and react with an antibody .
Are haptens antigenic and immunogenic when linked with a carrier molecule?
They are antigenic but not immunogenic .
Define antibodies .
A group of protein globuin glycoproteins and immunoglobulins present in the blood plasma that combine with the antigenic determinant that triggered its prodicton .
When is the constant region for the antibodies structure the same?
The same for antibodies of the same class .
How many and what type of chains is the antibody structure composed of ?
2 identical inside heavy chains and 2 identical outside light chains .
How are the chains of the antibody structure held together?
The 2 heavy chains and held by 2 disulphide bridges . The heavy chains are attached to the light chains by 1 disulphide bridge .
What causes the Y shape of he antibodies .
Hinge regions on the heavy chains which enable flexibility .
What are variable regions of the antibody structure?
Tips of the heavy and light chains which act as antigen binding sites .
What are hypervariable regions of the antibody structure?
Very tip of the light and heavy chains .
How many hypervariable regions do most antibodies have?
2
What is a unique feature of the IgG antibody?
The only antibody that can cross the placenta .
What is the purpose and main function of IgG antibodies?
Protect us against bacteria and viruses - high affinity to microbes at epitope sites and trigger complement system, enhance phagocytosis and neutralise toxins .
Wha is the general function of IgA antibodies?
Provides localised protection mucus membranes .
What is the general function of IgM anitbodies?
Causes lysis of microbes and helps agglutinated of red blood cells .
In what ways do antigen-antibody complexes neutralise or eliminate antigens?
Activation of complement systems by the classical pathway, phagocytosis through oposonisation, neutralisation by cross-linking molecules of toxins or viruses .
How are monoclonal antibodies made?
Antibody-producing B cells fuse with myeloma cells . This creates a hybridoma which is immortalised and antibody producing .
How are monoclonal antibodies used to find cancers?
Toxins are often placed on the tail of monoclonal antibodies and the toxins are then delivered directly to the cancer .
What causes the precipitation to occur in the precipitation ring practical?
The antigens (with 2 or more epitopes) become cross linked by the use of complimentary antigens to form a lattice. The antigens and antibodies must be in equal ratios.
What must be a feature for the precipitate to form in the precipitation ring practical?
The antigens and antibodies must be present in the same concentration.
Why is it necessary to use a series of antigen dilutions in the precipitation ring practical?
To ensure a tube contains a zone of equivalence (precipitate) for optimum complex formation. Enables semi-quantitate results to be recorded. Required due to the polyclonal nature of the antibodies.
What factors does the forming of a precipitate depend on in the precipitate ring practical?
The affinity of the antigen to the antibody - higher affinity = greater precipitate.
Ratio of antibody to antigen - must be in equal concentrations.
Why may no precipitate be present in the precipitate ring reaction?
If the optimum ratio of antibodies to antigens is not present no lattice and therefore no precipitate will form. The antigen must be in equal concentration to the antibody.
Define precipitin.
Soluble antibodies which react with soluble antigens to form a precipitate.
Define Precipitinogen.
Soluble antigens which induce the formation of precipitin.
Define lattice in terms of the precipitin ring practical.
The cross linking of antigens and antibodies to form and immunocomplex.
What is the equivalence zone in the precipitate ring reaction?
The zone where the concentration of antibodies and antigens is equal. A immunocomplex lattice can form. Precipitate is present.
What is the basic difference between Geel diffusion occurring in Oudin tubes and Ouchterlony plates?
Oudin tubes used single, one directional diffusion.
Ouchterlony plates use 2D diffusion.
What is the clinical significance of febrile antibodies?
Used to diagnose infections and diseases such as haemolytic anaemia.
Why does Agar jelly resist contamination with bacteria?
Agar is a polymer made up of subunits of galactose and red algae so cannot be easily degraded by micro-organisms.
What are semi-quantitative results?
E.g “Less than 5” “Between 5 and 20” “Greater than 20”.
Which method (Ouchterlony or Precipitation ring reaction) produces a more stable precipitate?
Ouchterlony
Are Ouchterlony or precipitation ring reactions quicker?
Precipitation
How does agglutination differ from precipitation reactions?
An insoluble antigen is used in agglutination whereas precipitation methods use soluble antigens.
Do precipitation methods use soluble or insoluble antigens and antibodies?
Both are soluble but form an insoluble complex.
Define inflammation (acute).
The local response of living tissue to any infectious agent.
Compare the onset times of acute and chronic inflammation.
Acute - rapid
Chronic - slow
Compare the cells used for acute and chronic inflammation.
Acute = Neutrophils Chronic = Lymphocytes, Monocytes and macrophages.
Compare the type of tissue injury which induces acute and chronic inflammation.
Acute = Mild Chronic = Severe and processingly worsening
What are the 5R’s / 5 steps to an inflammatory response?
Recognition (of the injurious agent)
Recruitment ( of inflammatory cells - leukocytes)
Removal (of the injurious agent)
Regulation (of the inflammatory response)
Resolution / repair
What are the two main overall processes that occur as part of acute inflammation?
Vascular changes
Cellular events
What are the vascular changes that occur during acute inflammation?
Vasodilation and increased vascular permeability.
How is vasodilation caused during acute inflammation?
Histamine hormone is used to expand the arterioles and increase the blood flow. This causes the tissue to become red and warm.
What process in acute inflammation causes the red and hot symptoms?
Vasodilation
What are the overall purposes of vasodilation and increased vascular permeability in acute inflammation?
The blood becomes more viscous so blood flow is slowed. This leaves time for the engorgement of small vessels.
What are the 4 ways that vascular permeability increases during acute inflammation?
Explain each one.
Contraction of the endothelial cells - causes gaps between endothelial cells to become larger and allows leakage of fluid, blood and proteins to move into the extravascular space.
Direct endothelial damage such - toxins and burns cause endothelial damage allow leakage.
Injury of endothelial cells due to leukocytes - neurophils adhere to the endothelial cells and damage them. Leads to leakage.
Transcytosis- increased transport of fluids and proteins in the intracellular channels. The channels are stimulated by vascular endothelial growth factors which promote leakage.
Explain how transcytosis can cause vascular permeability to increase.
There is increased transport of fluids and proteins into the intracellular channels. The channels are stimulated by vascular endothelial growth factors which promote leakage.
What are leukocytes?
A type of white blood cell. Often used in the inflammatory response.
What cellular events occur to cause acute inflammation?
Recruitment of Leukocytes.
Activation of Leukocytes leading to the process of destruction of invading cells and production of mediators.
What are the stimuli for acute inflammation.
Tissue necrosis - cells released from the dying cell site act as stimuli.
Infection
Trauma ( due to physical or chemical agents)
Foreign bodies (splinters etc)
Immune reactions
What is tissue necrosis?
The passive breakdown of order structure and functions of a tissue resulting in irreversible damage.
How are acute inflammation stimuli recognised by the host in general terms ?
They are recognised by receptor on antigen presenting cells and epithelial cells.
What 2 types of receptors recognise acute inflammation stimuli?
Toll like receptors
Inflammasomes
What do toll like receptors detect as part of the acute inflammatory response?
They detect microbial stimuli and pathogen products.
Where are toll like receptors present?
Plasma membrane and endosomes
What are endosomes?
Membrane bound vesicles.
What is the outcome of the use of toll like receptors in acute inflammation?
Results in the production of inflammatory mediators.
What do inflammasome receptors detect as part of the acute inflammatory response?
They recognise multi protein cytoplasmic complexes and products of dead cells.
What is the outcome of using inflammasome receptors in the acute inflammatory response?
They activate caspace-1 which activates mediators of leukocyte recruitment. The recruited leukocytes then phagocytose and destroy the injurious agent or dead cells.
Outline the life cycle of a B lymphocyte duding interphase.
G0- B lymphoid is small and nieve. Antigens activate B lymphocyte. G1- Genes within B lymphocyte are activated and DNA is synthesised. Lymphoblast S produced. G2 - Cell division.
What do B lymphocytes derive from and where are they produced?
Stem cells
Bone marrow
How do B lymphocytes move around the body?
Via the blood
Where are B cells stored ?
The lymphatic system
What part of the B cells allows activation by antigens?
B cells immunoglobulin on their membrane. This can be activated to induce differentiation.
How long do plasma cells generally survive for?
1-2 weeks
How long do memory cells generally survive for?
Decades
What do B lymphocytes divine into?
Plasma cells and memory cells
What are the 3 different types of lymphocytes ?
B cells, T cells, Natural Killer cells (NK cells).
Are B and T lymphocytes part of the specific or non-specific immunity?
Specific
Where do T and B cells migrate to from the bone marrow?
Lymphatic system
What are T and B cells activated by ?
Antigens
Are Natural killer cells part of specific or non-specific immunity?
Non-specific
Where are clusters of differentiation found?
Antigens on the surface of lymphocytes
How are CD antigens used to identify cell types which are present in a sample - outline the process.
Monoclonal antibodies are marked with fluorescent markers on their tail end. These monoclonal antibodies bind to the specific CD (cluster of differentiation) antigens on the lymphocyte surfaces.
The fluorescent colouring present will identify what cell types are present in the lymphocyte mixture because a colour complex is formed when the marked monoclonal antibody binds to a complimentary CD antigen.
What cell type are CD4 antigens used to identify?
Helper T cells
What cell type are CD8 antigens used to identify?
Cytotoxic T cells
What cell types are CD21 antigens used to identify?
B cells
Outline the life cycle of a T lymphocyte.
Stem cells differentiate into immature T cells in the bond marrow. These then migrate to the thymus gland via the blood.
In the thymus, the immature T cells differentiate in to cytotoxic, helper and regulatory T cells via a highly selective process.
They then travel via the blood to the thymus-dependent areas of the lymph nodes and spleen.
They remain here until being activated.
Which specific antigens can T lymphocytes recognise?
Antigens displayed alongside MHC molecules.
Which specific antigens can B lymphocytes recognise ?
All free antigens
What type of CD antigen markers do helper T cells have and what type of MHC antigens do they recognise?
CD4
MHC classII
What type of CD antigen markers do cytotoxic T cells have and what type of MHC antigens do they recognise?
CD8 MHC class I
