Adaptive Immunity Flashcards
What can a hematopoietic stem cell differentiate into?
A myeloid progenitor cell or a lymphoid progenitor cell
What can myeloid progenitor cells differentiate into?
RBC
Platelets
Neutrophils
Eosinophils
Basophils
Monocytes
Macrophages
What is the pathway of myeloid progenitor cell differentiation associated with?
Innate immunity
What can lymphoid progenitor cells differentiate into?
Lymphocytes
-T-cells (helper, regulatory, cytotoxic)
-B-cells -> plasma cells -> antibodies
Natural killer cells
What is the pathway of lymphoid progenitor cell differentiation associated with?
Adaptive immunity
What is unique about natural killer cells?
They are differentiated from lymphoid progenitor cells but are involved in innate immunity as instant killers
What are the 3 characteristics of adaptive immunity?
Detects vast repertoire of molecules
Receptors are generated by somatic recombination
Improved adapted response to repeat exposure
What is an antigen?
A foreign molecule, typically from a pathogen
What are the types of antigens recognized by B cells?
Proteins
Lipopolysaccharides
Lipids
Nucleic acids
What are the types of antigens recognized by T-cells?
Peptides derived from proteins
What is the difference between T-cell and B-cell detection of antigens?
T cells require antigen presentation by dedicated antigen-presenting cells while the BCR directly recognizes its cognate antigen
What are the two forms of adaptive immunity?
Humoral and cellular
What is humoral immunity?
Directed attacks against extracellular microbes mediated by B cells
B lymphocytes secrete antibodies that neutralize and eliminate microbes and microbial toxins
What is cellular immunity?
Directed attacks against intracellular microbes mediated by T cells.
T lymphocytes activate phagocytes and lymphocytes or kill infected host cells
What new properties do active B cells have that naive B cells do not?
Production of antibodies
Expression of receptors that recognize cytokines
How are humoral and cellular immunity distinctive?
They neutralize microbes in different locations
What is the purpose of T helper cells?
To activate macrophages to kill phagocytosed microbes
Boosts ability of the macrophages
What do cytotoxic T cells do?
Kill infected cells and eliminate reservoirs of infection
What 2 signals does activation of adaptive immune response need?
Antigen receptor binding to the antigen
Microbial or innate immune signals
Why can only certain BCR recognize certain antigens?
They recognize a limited number of antigens
If there is antigen detection, there is a reasonable affinity for that antigen to a microbe
What is clonal expansion?
When a BCR or TCR detects antigens the B cell or T cell undergoes multiple rounds of cell division, thereby expanding
What is the recognition phase of adaptive immunity?
Naive lymphocytes recognize corresponding antyigen
What is the activation phase of adaptive immunity?
Lymphocytes differentiate and start clonal expansion
What is the effector phase of adaptive immunity?
Differentiated lymphocytes initiate microbial elimination
via killing of target cells and production of antibodies
What is the decline phase of adaptive immunity?
After microbial elimination the signal for lymphocyte activation disappears
Most of the cells activated by antigen die via apoptosis
What is the memory phase of adaptive immunity?
The remaining cells are memory lymphocytes which may survive for months or years
Prior exposure to one antigen produces stronger responses to subsequent infections from the same antigen
Where are antibodies released?
Released from B cells into circulation and mucosal fluids upon infection
What do antibodies do?
Neutralizes microbes and microbial toxins
Stops microbes from gaining access to or colonizing host cells
What do antibodies not have access to?
Intracellular microbes
Where do antigen-presenting cells (APCs) reside?
In potential sites of microbe entry
What do APCs do?
Capture, process, and present antigen to T cells in peripheral lymphoid tissues
Why do T cells require co-receptors?
To assist antigen recognition
What do CD4+ helper T cells detect?
Antigens presented by professional APCs
What do CD4+ T cells do?
Secrete cytokines to activate other components of the immune response
What do CD8+ cytolytic T cells detect?
Microbial antigens presented by all nucleated cells and destroy the presenting cell
How do you bring the right lymphocyte together with its cognate antigen upon infection quickly enough to activate the appropriate immune reply?
The peripheral lymphoid organs concentrate antigens and lymphocytes to optimize interactions
What are the peripheral lymphoid organs?
Lymph nodes, spleen, mucosal and cutaneous lymphoid tissue
What is the lymphatic system?
A network that transports fluids from tissues through lymph nodes and ultimately to the circulatory system (initially to veins)
Excess IF is collected by the lymphatic system and is processed by lymph nodes prior to being deposited into the circulatory system
How does the lymphatic system differ from the circulatory system?
It is not closed and has no central pump
How does stuff move through the lymph system?
APCs drain from peripheral tissues into lymph nodes
T lymphocytes enter lymph nodes
APCs activate T lymphocytes
Lymphocytes exit lymph nodes and enter circulation, then exit circulation into inflamed tissue where they mediate microbial destruction
What part of the lymph node is rich in B-cells?
The cortex
What part of the lymph node is rich in T-cells and dendritic cells?
The paracortex
