Immune system and immune response Flashcards
Monocytes
Largest phagocyte, kidney been shaped nucleus, origionate from myeloid cell line, found in blood stream, enter tissue if infected, respond to bacterial infection, differentiate into macrophages or dendritic cells in tissue
Macrophages
From monoctyes, in tissue, phagocytosis of cellular debris, microbes and other foreign substances, help initiate adaptive immune reponse by presenting antigens and secreting factors to induce inflammation,
Dendritic cells
Link between innate and adaptive immune system, travel in blood and through tissue, following phagocytosis of pathogen it migrates to peripheral lymphoid organ to present antigen to T cell
Neutrophils
first line of defense, particularly against bacterial infections, most common, from myeloid stem cells, multilobed nucleus and many granules,
Eosinophils
granular leukocyte, from myeloid stem cells, mainly in tissues, parasitic infection, bi-lobed sausage-shaped nucleus
Basophil
granular leukocyte, myeloid stem cells, bi-lobed S-shaped nucleus, contains histamine granules, response to allergens
Natural killer cells
lymphocyte, non-specific immunity against cells displaying foreign pathogens, function more effectively alongside T helper cells
B plasma cell
large cells, abundant ER to produce large quantities of antibodies
Memory B lymphocytes
long lived, rapidly proliferate with help of T cells on re-exposure to same antigen, will then divide and differentiate into plasma cells to produce antibodies
T-independent B lymphocyte
Produce antibodies without T cell help, found in spleen and peritoneum, deal with encapsulated bacteria as can recognise these and produce antibodies
CD8 Cytotoxic T cells
Kill target cells by releaseing cytotoxic granules into target cell
Only recongise antigen on MHC I molecule present on all nucleated cells
Mainly kill virally infected cells, those with intracellular bacteria or tumorous cells
CD4 T helper lymphocyte
Help shape, activate and regulate adaptive immune response
Differentiate into many subtype
Activated when presented with peptide antigen on MHC II on APC surgace
Function of Th1, Th2, Th17 and Treg cells
Th1 - involved in macrophage activation
Th2 - production of antibodies and in anti-parasite response
Th17 - produce IL-17 (recruiting neutrophils and differentiation)
Treg cells - prevent cells self attacking, regulate immune system in peripheral lymphatic system
Memory T cells
Antigen specific, long-lived memory T lymphocytes following an infection, can quickly proliferate into large number of helper cells on re-exposure, low threshold for activation, provide immune system with memory
What are the primary lymphoid organs and their function?
Bone marrow, thymus
Lymphocytes origionate her: B produced and mature in bone marrow, further maturation in spleed/ lymph nodes, T lymphocyte precursors migrate from bone marrow to mature in thymus (important in preventing autoimmunity)
What are the secondary lymphoid organs and what is their function?
Lymph nodes: meeting point, lymph drains from tissues, antigens and bacteria collect here, where immune response is activated, filters lymph
Spleen: under rib cage, enlarges during immune response, resevoir of red and white blood cells, filters circulating blood, can also activate immune repsonse
Connected via blood and lymphatic vessels
Antibody Structure
Structure: 2 identical heavy chains and 2 identical light chains –> 2 antigen binding sites; disulphide bridges bind chains together, Fab region (fragment antigen binding, bind to pathogen) & Fc region (interacts with different immune cells and mediates funciton); hinge region gives flexability
Antibody function
Opsonisation: bind to pathogen to allow better recognition by pahtogen, phagocyte binds to Fc receptors initiating phagocytosis
Neutralisation: prevent pathogens from accessing cells by blocking parts of their suface
Complement Activation: clasical complement pathway activaed by some anitbodies, releases the opsonin C3b
Immune complexes: bind multiple antibodies and antigens together, limits antigens diffusing ability and easier to phagocytose
Antibody-dependent cell-mediated cytotoxicity
Inflammation
T lymphocyte development
Origionate from haemotapoietic stem cells in bone marrow which form thymocytes
Thymocytes leave bone marrow and travel to thymus via blood
Thymocytes undergo selection process in thymus: those with self-antigens are removed
T lymphocytes have T cell receptor specific to antigen
Surving T lymphocytes mature and leave thymus to circulate through peripheral lymphoid organs to encounter their cognate antigens to become activated
Activation of naive T lymphocytes
Naive T cells interact with ACPs which present antigen on MHC
T cells with CD4 co-receptor will bind to specific antigen presented on MHII molecule on APC and proliferates and differentiate into T helper cell
T cells with CD8 co-receptor bind to specific antigen presented on MHCI molecule on any nucleated cells and proliferate and differentiate into cytotoxic T cells
Basic innate immune response to extracellular bacterial infection or a viral infection
- Macrophages continually monitor for foreign pathogens and recognise them using Pattern Recognition Receptors (PRRs)
- Macrophage releases chemical signals (e.g. cytokines) to recruit more blood cells and remove bacteria via phagocytosis
- Dendritic cells, macrophages and monocytes phogocytose pathogens and move to lymph node where they present antigens to T-cells
- Complement cascade activated which supports other parts of the immune system
Interatiction of T helper lymphocytes with B lymphocytes
T helper cells release cytokines which help activate other B cells and getting them to differentiate into plasma cells and release antibodies
Cells and molecules involved in inflammation (5)
Clotting system: activation of plasmin resulting in fibrinolysis and release of bradykinin
Complement system activated (especially complement component 5s)
Activate mast cells which release histamine causing inflammation directly
Inflammatory lipids - released by mast cells
Cytokines (particularly IL-8 and TNF) - released by mast cells and other recruited immune cells
Inflammation as a protective response
Isolates damaged area - prevents metastasis of infection
Mobilises effector cells and molecules to the sites
Promotes healing and tissue repair in later stages
5 clinical features of inflammation
Rubor (redness), Calor (heat), Tumour (swelling), Dolor (pain) and loss of function
Inappropriate magnitude/ duration of inflammation contributes to diesease
Inflammatory response out of proportion or outlive threat, more damage to body than the infection would have caused, leads to loss of organ/ tissue function
Underlies many chronic diseases: cardiovascular disease with inflammation of blood vessels, Alzheimer’s, cancers
Macrophage/ neutrophil recognition and killing of pathogen
Recognition: variety of different surface receptors recognise key components of pathogen, cell has to be activated by both receptors and TLRs which recognise PAMPs on surface of pathogen
Killing: phagocytosis of bacteria, acidification, toxic oxygen-derived products, toxic nitrogen oxides, antimicrobial peptides, enzymes, competitors
Role of the lymphatic system
Returns fluid to heart, helps large molecules enter blood, helps with immunosurveilance
Lymph: what is it? how is it produced?
Fluid in lymphatic vessels and lymph nodes
Small proteins and fluid leak out of capillaries to form interstitual fluid, fluid which isn’t reabsorbed collect in lymphatic vesses –> lymph
Lymphatic system, vessels and drainage structure
Lymphatic system is the one way system of lymphatic vessels which collects lympth. Lymph collects in lymphatic capillaries travels through vessels to trunks and to ducts (using pressure from arteries and skeletal muscles). Drains lymph back into the blood at the right lymphatic duct to right jugular or right subclavian vein or thoracic duct dumps lymph into these junctions on the left. Here pressure is low making lymph more likely to flow in.
Role of lymph nodes
Tighly packed balls of lymphoid cells and protein
1. Unfiltered lymph (potentially containing pathogen) drains into lymph node
2. Pathogen detected by dendritic cell and present pathogen to B Cells
3. B cells activated and turn into plasma cell which produce anitbodies which exit the lymph node
4. Circulating T cells also collect here on the lookout
Basic adaptive immune response to extracellular bacterial infection or a viral infection
Role of the speen
White pulp: antibody-coated bacteria are filtered out, antibodies made by B cells, similar to giant lymph node recieving blood
Red Pulp: old blood cells are destroyed and their parts are recycled, keeps RBC and platelets available
IgA
Dimer (very small)
Prevalent in secretions
IgD
Monomer
On all B cells
IgE
Monomer
Present in parasitic infections and type 1 hypersensitivity
IgG
Monomer
Most abundant
Can cross the placenta
IgM
Pentameter
Largest
Present on all B cells
