The Immune System Flashcards
Role of macrophage and which type of immunity?
Effector cells of the innate immune system
They phagocytose bacteria and secrete both pro-inflammatory and antimicrobial mediators
Role of dendritic cells and which type of immunity?
Antigen-presenting cells of the innate immune system
They capture, process, and present antigens to lymphocytes to initiate and regulate the adaptive immune response
Role of neutrophils and which type of immunity?
Innate immune system
Phagocytoses pathogens, generating toxic superoxide and its metabolites, releasing antimicrobial peptides, and forming neutrophil extracellular traps (NETs).
Role of NK cells and which type of immunity?
Innate immune system
Kill virally infected cells via the directed release of lytic granules or by inducing death receptor-mediated apoptosis via the expression of Fas ligand or TRAIL
Lytic granules = perforin or granzymes
Which type of immunity does the complement system act in?
Innate immune system
Role of inflammatory cytokines/chemokines and which type of immunity?
Innate & adaptive immune system
Intercellular messengers send soluble regulatory signals that initiate or prevent inflammatory responses to pathogens and injury
Difference between cytokines and chemokines?
Cytokines = large and diverse group of pro- or anti-inflammatory factors
Grouped into families based upon their structural homology or that of their receptors.
Chemokines = group of secreted proteins within the cytokine family whose generic function is to induce cell migration
Role of T helper cells and which type of immunity?
Adaptive immune system
Stimulate B-cells to make antibodies and help killer cells develop
Role of cytotoxic T cells and which type of immunity?
Adaptive immune system
Cytotoxic CD8 T cells kill by releasing two types of preformed cytotoxic protein:
granzymes, which seem able to induce apoptosis in any type of target cell
pore-forming protein perforin, which punches holes in the target-cell membrane through which the granzymes can enter.
Role of B cells and which type of immunity?
Adaptive immune system
Producing antibodies, activate T cells via APCs, supporting other mononuclear cells and contributing to inflammatory pathways directly via cytokine production
Role of antibodies and which type of immunity?
Adaptive immunity
Binds to pathogens.
Activates the immune system in case of bacterial pathogens.
Directly attacks viral pathogens.
Assists in phagocytosis.
Antibody provides long-term protection against pathogens because it persists for years after the presence of the antigen.
What makes up the complement system?
Variety of distinct plasma proteins
What does the complement system do?
Rupturing cell wall of bacteria = classical complement pathway
Opsonize antigens = alternative complement pathway
Induce inflammatory responses = lectin pathway
What is haematopoisesis?
Formation and development of WBCs and RBCs from pluripotent hematopoietic stem cells
What do the hematopoietic stem cells differentiate into?
Lymphoid progenitor
Myeloid progenitor
What are the 4 things myeloid progenitors differentiate into?
Erythroblasts
Monocytes
Platelets
Granulocytes
What do monocytes differentiate into?
Macrophages
Dendritic cells
What do lymphoid progenitors differentiate into?
B & T cells
NK cells
Dendritic cells
Where are dendritic cells differentiated from?
Both lymphoid progenitor & myeloid progenitor
Myeloid progenitor -> Monocyte -> dendritic cell
Where do T & B cells go once they mature?
Move to secondary lymphoid organs
What does immunocompetent mean?
Lymphocytes can respond to the antigen
When do lymphocytes become immunocompetent?
Once they have matured
What is the main function of secondary lymphoid organs?
Sites of interaction between immunocompetent cells and antigens = TRAP ANTIGENS
Where do lymph nodes trap antigens?
Intracellular fluids
Where do the antigens the spleen trap come from?
From blood
What does MALT stand for?
Mucosa-Associated Lymphoid Tissue
What does GALT stand for?
Gut-associated lyphoid tissue
Where do the antigens MALT traps come from?
Mucous membrane surfaces
What are the secondary lymphoid organs?
Spleen
MALT
GALT
Peripheral lymphoid
Name the 4 MALTs
Nasopharangeal
Tonsilar
Broncchial
All lymph nodes
What fluid turns into lymph?
Interstitial fluid = ECF
Role of the lymphatic system?
Maintenance of fluid balance
Enhancement and facilitation of the immune system
What does the collecting lymphatic vessel have?
Valves
How do lymphocytes enter the lymph node?
High endothelial venule cells
Where does the efferent lymphatic vessel come from and lead to?
From peripheral lymph node
To thoracic duct
Where does thoracic duct drain into?
Drains into subclavian vein
Drains all lymph from lower half of body
Do blood and lymph mix?
Not directly = interact across thin cellular layers with high surface area
What is the B cell area in the lymph node called?
Lymphoid follicles
What makes up a lymphoid follicle?
Germinal centre
Mantle layer
What is the T cell area in the lymph node called?
Paracortex
Are high endothelial venules found in all secondary lymphoid organs?
No, they are not found in the spleen
Where blood exits through open arterioles and enters the red pulp
What is recirculation important for?
Organised immune surveillance
Who discovered the immunological importance of lymphocytes?
James L. Gowans identified lymphocytes as the cellular units of clonal selection in adaptive immunity
What was James Gowans experiment and conclusion?
Collected lymphocytes from thoracic duct & labelled them with radioactive isotopes
Noticed they would dissapear from circulation = when they would go to secondary lymphatic organs
What does PAMPs stand for?
Pathogen-Assocaited Molecular Patterns
What are PAMPs?
Conserved molecular structures produced by microorganisms and recognized as foreign by the receptors of the innate immune system
Name some pattern recognition receptors
Toll-like receptor
Nod-like receptors
C-type lectin receptors = mannose receptors
T receptor structure and location?
Found only on cell membranes surface
Most common = alpha-beta
Also gamma-delta
B receptor structure and location?
Transmembrane
Made up of 2 heavy and 2 light chains joined by disulfide bonds
Each chain has a constant and variable region
Features of Innate Immunity
Specific for PAMPs = limited diversity
Respond rapidly = in place before infection
NO memory
Features of Adaptive Immunity
Highly specific and diverse
Adapt to specific infection
Needs longer time to respond - clonal expansion
MEMORY
What are the two defence mechanisms of the immune system?
Cellular Defence Mechanism
Humoral Defence Mechanism
What makes up the cellular defence mechanism?
Phagocytosis = cell eating
Cytotoxicity = cell killing
What makes up the humoral defence mechanism?
Complement = MAC
Antibodies
What defence do antibodies give us?
Humoral defence mechanism
Neutralization
Opsonization
Complement activaiton
What are the 4 granulocytes?
Neutrophils
Basophils
Mast cells
Eosinophils
