Overview of the immune system Pt 2 Flashcards
Timing innate
First line of defence
Fast
Non specific
Receptors innate
Use to detect pathogens
Encoded in Germaine
Limited number —> macrophages have same receptors
Unchanging
Key cell types innate
Phagocytic cells = macrophages, neutrophils, dendritic cells
And others
Actions innate
Induces local inflammtion
Responses to repeat infection innate
Same each time
Major components innate
Barriers = physical and chemical, like skin
Phagocytes
Some pattern recognition molecules
Timing adaptive
Slower to develop = 5-6+ days
About a a week
Receptors adaptive
Use randomly generated antigen receptors s
Huge diversity of receptor specificities
Highly specific to individual molecules
Key cell types adaptive
Lymphocytes
B AND T CELLS
Actions adaptive
Responsible for specific immune response
Most fo times clear infections
Result in memory sometimes
Responses to repeat infections adaptive
More rapid and effective With each subsequent exposure
Must be infected by same exact thing each time
Major components adaptive
T and B lymphocytes
Antigen specific receptors
Antibodies
Phases of immune response - describe
Many phases
Takes time
Innate immune response fast and lasts only days
Adaptive takes longer but lasts longer
What does innate immune response start with
Breach of epithelial layer
Body must be exposed to pathogen
Immune cells recognize non self
Macrophages and dendritic cells = sense pattern common amongst pathogens
What do immune cells express
Prrs
What are prrs
Pattern recognition receptors = provide initial discrimination between self and non self and recognize broad categories of molecules that are commonly found in pathogens = PAMPS
Recognize patterns
What are pamps
Pathogen associated molecular patterns
Common foreign structures that characterize whole groups of pathogens = part of many microorganisms but not part of host body’s own cells
Cell wall of bacteria = lipopolysaccharide, rna viruses = double stranded dna, we do not have this in our own body’s
What do macrophages express
Several receptors that allow them to recognize diff pathogens = binds many diff pamps
What happens when activate prrs axctivated
Now bound = know there is a pathogen, and something must be done
Activate innate immune cells = triggers local inflammation
Activation of prrs on cells like macrophages = directly induce effector functions on these cells = phagocytosis
Cells amplify immune response by producing ifnalmmtiory mediators = cytokines and chemokines
What do immune cells induce
Triggers inflammatory response by producing mediators = cytokines and chemokines
Hallmarks inflammation
Redness
Heat
Swelling
Pain
Bc all molecules entering and vasodilation
Describe whole process inflammtion
Macrophages phagocytosed pathogen = releases cytokines and chemokines
These cells induce inflammatory response and attract cells in circulation = chemokines can bind receptors of blood vessels and cells in circulation
Molecules binding = vasodilation and increased vascular permeability = causes inflammation, immune cells enter site of infection, also fluid enters, lining loser = get hallmarks inflammation
What does pathogen detection lead to
Activation of immune cells
Dendritic cells play key role = potent apcs
Detect Pathogens = pamps by receptors = prrs
Leads to dendritic cell activation
What links innate to adaptive
Dendritic cells
Describe what dendritic cells do
Travel from site of infection to local secondary lymphoid tissue then here interact and activate T cells
Once activated = mature by receptor binding
Naive to mature dendritic cell = presents antigens, match antigen to cell, recognizes specific T cell = now activated
Links innate —>adaptive
Describe t and B cell activation
Occurs in lymph node
One activated, subset T cells help activate B cells
Activated b and T cells - become effector cells = ready to fight
How is T cell activated
3 crucial signals
APCs activate T cells
Happens through 3 signals = need to complete activation, through interaction of specific molecules = receptors and cytokines
Happens in peripheral lymphoid tissue =lymph node
Name 3 signals that activate T cells
Activation
Survival
Differentiation
Describe basics of antigen presentation
Epitope of antigen can be a specific peptide buried within a protein
Antigen/epitope is present using specific molecule = major histocompatibility complex = Mhc= interacts with tcr
Only if on mhc, then see if fits receptor
Describe activation of adaptive immunity
Antigen specific cells activated in secondary lymphoid tissues= lymph nodes
Cells = T cell and B cell
What is antigen specificity determined by
Receptors
T cell = tcr
B cell = bcr, aka antibody aka immunoglobulin
Describe antibodies
Secreted immunoglobulin molecules
Made by b lymphocytes and it’s progeny plasma cells
Binds antigens
Present in serum = fluid component of blood, circulating
Do all antibodies reognize the same epitopes
2 antibodies can recognize diff epitopes on same antigen
Bc so very specific
Describe difference in b and T cells = origin/maturation
B cells arise and mature in bone marrow
T cells arise from bone marrow progenitors but are generated and mature in thymus
Describe difference in b and T cells = receptors
Bcr can be membrane bound or secreted (antibodies)
Tcr only exits as membrane bound
Describe difference in b and T cells = recognition
Tcr can only recognize small pieces of antigen bound to molecules of MHC on the surface of apcs
Bcr can recognize ag in natural form = do not need to be processed by dendritic and presented on mhc
Describe specificity of bcr and tcr - gen
Individual b and T cells each have individual specificity for a single antigen
Each lymphocyte expresses many identical copies of one receptor with specificity for one antigen
Huge diversity of lymphocytes = each with own specificity
Theoretical potential to response to any antigen that may come along
Describe specificity of bcr and tcr - how
Accomplished by rearranging and editing genomic dna that encodes the antigen receptors expressed by each b and T cell = creates diversity
What happens during dev
If lymphocyte reacts to self antigen = eliminated
Self reactive cells removed
Do not want autoreactive lymphocytes
Describe clonal selection
When b or T cell interact with its specific antigen = selected and becomes activated
Activation results in prolife = produces large number of clones,= each reactive against antigen that initially stimulated original lymphocyte= differentiation
Now becomes effector cell = mature now
What happens when egress to site of infection
Effector cells now —> once t and B cells are activated in lymphoid organs = becomes effector cells that can fight infections
Happens through both humoral and cell mediated activities —> then leave lymph node to site of infection
What does humoral immunity use
Combats pathogens via antibodies
What does cell mediated immunity involve
Primarily T lymphocytes
Describe cell mediated immunity
Mediated by T cells
Contribute to adaptive immunity in many ways
Many diff T cell subsets can get activated depending on the situation and exert a variety of effector functions
Describe cell mediated immunity - general effector functions
Some help activate B cells = follicular t helper cell, role = actiavte B cell
Some help activate macrophages = boost activity
Some kill infected cells directly = cytotoxic
Describe humoral immunity
Mediated by antibodies produced by B cells
Contribute to adaptive immunity by producing specific antibodies
Antibodies = diff types, act in diff ways, involved in clearing and/or neutralizing antigen
Covers pathogen so cannot bing to something else and replicate, help macrophages or phagocytic cells phagocytose
Describe regulation and memory
Hopefully after infection = downregulation of lymphocytes and immunological memory
What is immunization
Deliberate induction of an adaptive immune response
Describe active immunization
Natural = natural infection
Induced = vaccination
Describe passive immunization
With cells and/or molecules that mediate immunity
Natural = mother to fetus transfer of antibodies
Induced = monoclonal antibody therapy
