Overview Flashcards
Innate Immunity have cells that arise from what?
myeloid progenitor cells
What type of immune cells recognize general features of some pathogens such as repeating subunits that are common to many organisms?
innate immunity
General features that the innate immune system recognize are known as what?
PAMPS - (pathogen-associated molecular patterns)
PAMPS are recognized by what?
PRRs (pattern recognition receptors) that are found on a variety of immune cells
T/F Innate cells recognize signals from the acquired immune response that modulate their responses
true
How do innate cells help to initiate acquired immune cells?
innate cells (macs, dendritic cells) help by processing and presenting antigen to lymphocytes
What are the cells that mediate acquired immune responses?
lymphocytes
How are specific antigens recognized?
the recognition of specific sequences of amino acids, epitope or antigenic determinant
How is immunological memory provide a rapid response upon re-exposure to a pathogen?
upon encounter with specific epitope, lymphocytes produce protein factors (cytokines) to “help” other lymphocytes as well as regulate the activities of innate cells
Where is the site where all elements of the blood are derived from one type of progenitor cell? What is this specific cell called?
Bone marrow
pluripotent hematopoietic stem cell (hSC)
hSC give rise to 2 progenitors that give rise to the rest of the immune system. What are they?
- myeloid progenitor
- common lymphoid progenitor
The myeloid progenitor is the precursor for what? What type of immunity do these cells provide?
- granulocytes
- macrophages
- dendritic cells
- mast cells
Innate immunity
What is the group of cells that make up most of the innate immune system which are polymorphonuclear cells? What are the types of these cells?
granulocytes
- neutrophils
- eosinophils
- basophils
What are phagocytic cells that help activate bacteriocidal mechanisms?
neutrophils
What ar cells that kill antibody-coated parasites?
eosinophils
What type of granulocyte has an unknown function but is very similar to eosinophils?
basophils
What cell stems fromthe myeloid progenitor that are scavenger cells that have receptors for a variety of structures that are common to infectious agents?
macrophages (macs)
What cells play an important role in initiation of acquired immune responses?
macrophages
The immature circulating form precursors of macs are what?
monocytes
What are cells that are the most potent stimulators of T cell responses?
What is an important characteristic of these?
dendritic cells
branched, dendritic morphology
What cells take up antigen at the sites of infection/inflammation? Where do they take the antigen after and to what?
dendritic cells take up antigen then return to 2ndary lymphoid tissue to present antignes to naive T cells
What cells stem from myeloid progenitors degranulate to release histamine? What type of hypersensitivity are they associated with?
mast cells
associated with type I hypersensitivity rxns
Describe how macrophages and dendritic cells help initiate the development of acquired immune responses
- take up protein antigens
- process antigen (cut it into pieces)
- present antigen to naive T cells
- initiation of acquired immune responses
What cells have IgE receptors on their surface so that their activity can be modulated by acquired immunity?
mast cells
What gives rise to T cells and B cells?
common lymphoid progenitor
What gives tise to the Natural killer cells?
common lymphoid progenitor
Of the cells that come from the common lymphoid progenitor, which express receptor molecules on their surface and which do not?
T cells and B cells express receptor molecules on their surface to allow them to specifically recognize forein antigens
Natural killer cells (NKs) do NOT express antigen specific cell surface receptors
T/F all cells of the immune system originate from the bone marrow
Where do cells of the immune system circulate?
blood and lymphatic system
Describe where lymphocytes are generated and where they mature
- generated in bone marrow from common lymphoid progenitor cells
- migrate to lymphoid organs where they differentiate or mature
What are organized tissues where lymphocytes interact with non-lymphoid cells (antigen presenting cells or APC)?
lymphoid organs
What are the 2 main actions that occur in the lymphoid organs?
- development
- initiate of adaptive immune respones
Where do lymphocytes develop and mature?
central lymphoid organs or primary lymphoid organs
Where do T cells originate? B cells?
Where do T cells mature? B cells?
Both originate in bone marrow
T cells mature in thymus; B cells mature in bone marrow
Where are adaptive immune responses initiated?
peripheral lymphoid organs (2nd lymphoid organs)
What are the 2 actions that take place in the peripheral lymphoid organs?
- designed to trap antigens
- facilitate presentation of these antigens to lymphocytes
What is the peripheral lymphoid organ that colelcts antigen from the blood? What is its main function?
spleen
dispose of dead RBCs
The spleen is made up of red pulp and white pulp. Describe them
red pulp=> site of RBC disposal
white pulp=> lymphocytes surround arterioles entering the spleen
- white pulp divided into periarteriolar lymphoid sheath (PALS) which contain primarily T cells with flanking B cell corona
What are highly organized lymphoid tissues that collect antigen from lymphatics? Describe the process to reach this peripheral lymphoid organ
lymph nodes
- lymphatic vessels collect extracellular fluid from tissues
- return it to bloodstream
- lymph is continuously produced by filtration of blood
Describe the location of B cells and T cells w/in lymph nodes
B cells localized in follicles
- T cells distributed more diffusely in surrounding paracortical areas called T cell zones
Where are B cells undergoing intense proliferation? What occurs before this proliferation begins though?
Germinal centers
only following antigenic stimulation with T cell help
What tissues are associated with GALT (gut associated lymph tissue)? What is the function of these tissues?
tonsils, adenoids, appendix, Peyer’s patches
function is to capture antigen from eipthelial surfaces of GI tract
What tissue are the most important GALT tissues and have specialized cells called M cells? What is the fxn of M cells?
Peyer’s patches
M cells collect antigens along intestinal mucosa
Describe the lymphocyte follicle of Peyer’s patches
consists of large central dome of B cells surrounded by smaller numbers of T cells
What types of tissues are similar but diffusely organized lymphoid tissues that protect respiratory epithelium?
BALT (bronchial associated lymph tissue)
MALT (mucosal associated lymph tissue)
What are the 3 most important actions of the innate immune system?
- prevent most infectious agents from invading host
- clears most infectious agents
- control infections
Describe the link between the primary lymph and 2nd lymph organs
inflammatory responses facilitate uptake of antigen by phagocytes and increase the flow of lymph toward draining lymph tissue
this facilitates antigen transport to 2nd lymph organ
Describe the central principle of adaptive immunity
clonal selection of lymphocytes
- lymphocyte is stimulated by binding of its receptor to its cognate antigen
- lymphocyte is activated to proliferate
- proliferation gives rise to many new clones that bear identical antigen receptor specificity
T/F lymphocytes express receptor molecules that have highly specific binding characteristics
True
T/F each antigen-specific receptor expressed on an individual lymphocyte is identical
true
Describe the lymphocyte repertoire
each lymphocyte can potentially bind to a different specific component of infectious agents
Describe self tolerance
immune system removes most lymphocytes that bear receptors tha bind “self” antigens which will prevent immune system from attach host tissues
How is the diversity of lymphocyte receptor molecules generated?
somatic recombination
Describe the somatic recombination
Ig genes that code for lymphocyte receptors consist of a series of gene segments that are randomly recombined to generate complete coding regions for antigen-binding portions (variable domains) of lymph receptor molecules
What are the 2 antigen receptor of lymphocytes of the acquired immune system?
B cells and T cells
Which antigen receptor lymphocyte are produced and secrete antigen-specific antibody molecules?
B cells
***humoral immunity or antibody-mediated immunity***
Describe the B cell receptor
surface expressed antibody molecules serve as the B cell receptor and bind to particulate or soluble proteins in native or denatured conformation
What can antibodies(Abs) bind to?
bind to carbohydrates, nucleic acids, small chemical cmpds
B cell receptors have 2 antigen binding sites upon activation that will produce large quantities of antigen specific Abs. What will the result of these bindings produce?
Bind to the specific antigen then
- either neutralize the antigen (toxin/infectious)
- activate effector mechanisms that remove/destroy antigen
What is the secreted for of the B cell receptor?
antigen specific antibodies
What are lymphocytes that recognize peptide fragments of protein antigens presented on MHC molecules?
T cells
T/F T cells express antigen specific receptor (TCR) on surface and secrete these receptor molecules
What type of binding site is present on these receptors?
False, but do not secrete these receptor molecules
receptors have a single antigen-binding site
Describe B cell activation
- (1st signal) BCR binds to cognate antigen
- B cell endocytoses the antigen, breaks it into pieces
- presents antigen to antigen specific T helper cell
- (2nd signal) T helper cell supplies cytokine signal to B cell that activates B cell to proliferate, differentiate, make Abs
Describe T cell activation
specifically recognize peptide fragments of antigens that are presented to T cell by APC (macs, DCs, B cells)
- (1st signal) binding of cognate peptide antigen must be followed by
- (2nd signal) co-stimulation signal by APC
What are the 3 types of professional APCs?
- macrophages
- dendritic cells
- B cells
What actions must the professional APCs be able to do?
- able to take up antigens
- antigen processing
- antigen presentation (present peptides on surface to T cells)
What are peptide antigens presented on the surface of the APC with?
bound complex with either MHC class I or II molecule
T/F MHC class I and II molecules bind very tightly to many different peptides in a non-specific way
True
T/F TCR can only bind to peptides that are presented on MHC molecules
When B cells encounter their cognate antigen and become activated, what occurs?
proliferation, differentiation, produce large quantities of antigen specific antibodies
T/F isotypes of Abs have different functions
true
What action of B cells use antibodies can neutralize some pathogen derived toxins and some pathogens?
neutralization
Which actions of Abs coat antigens which facilitates the uptake of antigen by phagocytes or NK cells?
opsonization
Describe complement activation of B cells
some Abs bound to specific antgen serve as a receptor for 1st component of classic complement system
fix complement which facilitates destruction of antigen
Abs play important roles in activation and activity of what 2 innate immunity cells?
activation of NK cells for antibody-dependent cell-mediated cytotoxicity (ADCC)
vital role in activity of mast cells
What are the primary populations of T cells?
CD8 T cells
CD4 T cells
Which T cell recognizes peptide antigen presented on MHC class I molecules? Class II?
MHC class I => CD8
MHC class II=> CD4
Describe how CD8 T cells form armed effectors
once activated via recognition of cognate peptide: MHC I complex and costimulation by APC => CD8 proliferates and progeny cells differentiate into armed effector CD8 T cells
What is the only purpose of armed effector CD8 T cells? What is the other name of these cells?
kill cells that have cognate peptide: MHC I complex on their surface
Cytotoxic T cells or killer T cells
All nucleated cells in the body express what type of MHC molecules? What else do they present? What do these allow?
MHC class I
peptides from intracellular pathogens infecting cells
These complexes allow for ctyotoxic T cells to target infected cells for destruction
Describe how CD4 T cells secrete cytokines
- CD4 T cell encounters cognate peptide: MHC II complex receives proper costimulation
- CD4 proliferates and differentiates into armed effector T cells
- armed effector T cells secrete cytokines that modulate activity of other immune cells
these are helper T cells
CD4 T cells can differentiate into Th1 and Th2. Describe the actions of these
Th1=> supply cytokine signals to macs to upregulate activities of macs that increase ability to kill ingested bacteria and present peptide antigens
Th2=> promote Ab-mediated immune responses and help with B cell activation to supply cytokine signals that stimulate B cells to produce Abs that help with extraceullar pathogens via neutralization and complement fixation
Which helper T cell helps B cell activation and secrete cytokines that stimulate B cells to produce antibodies for opsonizing pathogens?
Th1 CD4 cells
Which T cell helps stimulate responses that are most effective for destroying intracellular pathogens?
Th1 CD4
Which T cell help B cells produce Abs to eliminate extracellular pathogens? What actions are associated?
Th2 CD4 cells
neutralization and complement fixation
What are the 2 common ways in which the body’s immune defenses fail?
- evasion and subversion of immune system by pathogens (various mechanisms)
- inherited immunodeficiency diseases (single gene mutation can result in profound immunodeficiency)
What are the 3 common unwanted responses of the immune system?
- hypersensitivity rxns (over-rxn of immune system such as acute allergies, contact hypersensitivities, immune complex diseases)
- autoimmunity - breakdown of safeguards that prevent immune response to self-tissue
- graft rejection - by product of safeguards but reject when transplant occurs due to different MHC molecules thus immune system rejects it
What precursor cell is involved in platelet formation and wound repair? What does it produce?
megakaryoyte
thrombocytes
What cell has an important role in clearance of immune complexes from circulation? What type of transport is involved?
erythrocytes
oxygen transport
What cell has a primary role to expel parasite pathogens from the body?
mast cells
Describe the correlation of gE receptors and mast cells?
have high affinity IgE receptors on surface that they get from circulation and use them as antigen-specific receptors
What cell is involved in expulsion of parasites from body through release of granules containing histamine and other active agents?
mast cells
What professional APC are involved in activation of T cells and initiation of adaptive immune responses?
Dendritic cells
What is an antigen?
a foreign determinant that can be found on the surface of a pathogen that can be in many forms such as proteins, carbohydrates, and lipids
Pattern recognition receptors
Which immuno cells recognize only protein determinants?
T cells
Which cells of the innate immune system are derived from common lymphoid precursor but bear no antigen specific receptor?
NK cells
Describe the roles of NK cells in both innate and acquire immune responses
- kill some virally infected cells
- effector cells of ADCC
What are the 3 roles of the macrophage (macs)?
- has many pattern-recognition receptors that allow it to recognize, phagocytose, and destroy microorganisms
- is also a professional antigen presenting cell
- has complement and Fc receptors that allow it to find and destroy opsonized microbes
Where are a majority of immune cells found?
the gut or GALT
Where are T cell and B cell proliferation occuring after an initial immune response triggers an adaptive immune response?
germinal centers
What are the 4 postulates of clonal selection?
- each lymphocyte bears single type of receptor w/ unique specificity
- Intxn bw a foreign molecule & lymphocyte receptor capable of binding that molecule w/ high affinity leads to lymphocyte activation
- differentiated effector cells derived from activated lymphocyte will bear recptors of identical spec to those of parental cells from which that lymphocyte was derived
- ymphocytes bearing receptors specific for ubiquitous self molecules are deleted at earge stage in lymphoid cell development therefore absent from repertoire of mature lymphocytes
T/F only 1 B cell expresses one specific type of Ab
true
What is a unique mechanism that allows generation of tremendous repertoire of antibody and T cell receptor specificities?
somatic recombination
Describe the activation of B cells and the signals resulting from activation of B cells?
CD4 or Th cells recognize complex of peptide antigen with MHC II and activates B cell
Effector Th2 cells interact w/ antigen-specific B cells in lymphoid tissue
What signals result in activation of T cells?
Naive CD4 T cell recognizes peptide + MHC II
Naive CD8 T cell recognizes peptide + MHC I
What is the most important function of Abs?
coating for opsonization
How do Killer T cells Help Fight Infection?
cytotoxic T cell recognizes complex of viral peptide with MHC I and kills infected cell
Describe the process which Th1 cells kill intravesicular bacteria
Th1 cell and infected macs come together
T cell binds to a, and acitvates macrophage
kill bacteria
