L14 Adaptive Immunity Flashcards
Characteristics of adaptive immunity
Highly specific
Immunologic memory
Rapid response to second antigen exposure
What are the types of active immunity and describe them
Natural:state of resistance following contact with foreign antigen (clinical or subclinical infection)
Artificial: through killed or attenuated organisms by vaccine
What are the types of passive immunity and describe them
Natural: through placenta(igG)
Breastfeeding(igA)lasts 4-6 months
Artificial: administration of preformed abs (antitoxin when illness is attributable to exotoxins) eg botulism
What are the cells involved in specific immune response and what do they do
Macrophages:phagocytic cells—-APC
T lymphocytes: intracellular microbes
B lymphocytes: humoral immunity
What are the subsets of t cells and their function
CD4 effector cells: th1,th2,th17
Can become t reg cells if exposed to TGF-B (suppress t cell responses)
CD8 positive cells: effector cytotoxic t cells, kill infected host cells as virus infected or tumor cells by delivery of toxic granule content(perforin and granulysin)
What do b cells carry on their surface and what is their function
IgM act as receptors for a specific antigen
Immunity directed at extraceullar pathogens
Humoral immunity
Immunity depending on intracellular pathogens
Cell mediated immunity
Describe the process of antigen presentation
Proteins are internalized by apcs
Undergo partial proteolysis or denaturation
Peptide fragments become expressed on surface of APC as MHC complex
Recognized by specific t cell
Examples of APC
Macrophages
Langergans cells of the skin
Dendritic cells
B lymphocytes
What are the 3 signals needed for t cell activation
1-t cell receptor interacts with an MHC peptide complex on APC
2-co stimulation: b7 protein on APC binds with CD28 on t cell
3-cytokines delivered by APC
Th-1 cells
Stimulated by intracellular pathogens
Secrete IL-2 and IFN-y
What does IL-2 do and IFN-y
IL-2 acts on CD8 cells and enhances their proliferation and differentiation
IFN-y amplifies th-1 response and activates macrophages
Th-2 cells
Activated in response to large extracellular pathogens
Produce IL4 ,5,13
Promotes humoral immunity+causes class switching
Th17 cells
Against fungal infection
Describe t cell dependent activation of b cells
B cells recognize their specific ag by surface membrane ig receptors
Act as APC and ingest large proteins and digest them—display MHC ll molecules for recognition by t helper cells
T helper cells secrete cytokines to activate b cells
Class switch after proliferation
Memory cells
Describe t cell independent b cell activation
Polysaccharides,lipopolysaccharides and lipids= t cell independent antigens
Contain multiple identical epitopes that cross link ig receptors on b cell providing signals that stimulate b cell responses
Dominated by IgM production
Short lived plasma cells
No memory cells
How are t cytotoxic cells activated
When they recognize their antigen on the surface of a target cell along with MHC class l mol
Also by effect of cytokines (IL2)
Kill viral infected and tumor cells
What is the primary response
Ab produced after first encounter with pathogen
Serum conc rises for several weeks and then declines
First IgM then IgG and IgA
IgM declines before IgG
What is the secondary response
More rapid Generates higher levels than primary response Due to presence of memory cells IgM is same IgG is more and persists longer
Describe the interaction between innate and adaptive immunity
▪️Phagocytic cells process and display antigens to facilitate stimulation of specific t lymphocytes
▪️Macrophages secrete cytokines that help trigger the initiation of specific immune responses
▪️t cells produce cytokines(IFN-y) which enhance microbicidal activities of phagocytes
▪️ab produced by plasma cells bind to pathogens and assist with phagocytosis and ab dependent cell mediated cytotoxicity
