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57 Cards in this Set
- Front
- Back
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when are your t cells formed
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all of your T cells are formed by the time you are born
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where do B cells mature
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in primary lymphoid tissue (bone marrow) before they encounter antigen
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how does B cell formation differ from T cell formation
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T cells are all formed by the time you are born
B cells are constantly shuffling Ig and forming new combinations throughout your life |
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what are the stages of B cell development
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antigen independent
antigen dependent |
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what occurs in B cell antigen independent development
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rearrangment of immunoglobins in primary lymphoid tissue
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what occurs in B cell antigen dependent development
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occurs in 2ndary lymphoid tissue when the B cell encounters antigen, T cells are present in the 2ndary lymphoid tissue ready to help B cells
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when do T cells help B cells in development
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antigen dependent step
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why is there no antigen dependent step for T cells
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because all your T cells are formed by the time you are born or shortly after birth
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what are the properties of hematopoietic stem cells
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unlimited ability to proliferate
multipotent - they can form any cell in the blood depending on cytokine environment except liver and brain cells |
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why aren't hematopoietic stem cells totipotent
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they are not able to form ANY TYPE OF CELL such as liver/brain cells
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what is required for stem cells to renew
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SCF
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what is the 1st thing that stem cells do
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differentiate into myeloid and lymphoid cells
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what do lymphoid cells make
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lymphocytes ( B and T cells)
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what is required for lymphoid development
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IL-7 (Interleuken 7)
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what is required to make erythrocytes
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EPO
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what is needed for the formation of macrophages/dendritic cells
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GM-CSF ( Granulocyte Macrophage colony stimulating factor)
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where does T cell development occur
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in the thymus
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what are the major regions of the Thymus
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cortex and medulla
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how is the thymus a perculator
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thymocytes (immature T cells) perculate through the thymus making contact with different cell types in the thymus in order to select for certain TCR
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how is the thymus a nurturing environment
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it secretes peptides that promote T cell differentiation
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where do developing thymocytes enter the thymus
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cortex (top)
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what are some of the different cells contained in the thymus
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dendritic cells
nurse cells macrophages cortical epithelial cells medullary epithelial cells |
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where are cortical epithelial cells located
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cortex
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where are dendritic cells and macrophages located
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medulla
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where are nurse cells located
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cortex
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what do nurse cells do
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secrete hormones which promote thymocytes to undergo T cell differentiation
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how is T cell differentiation accomplished
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by changes in surface markers
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what surface markers do T cells have when they first enter the thymus
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they are double negative CD4- and CD8- meaning they don't have either marker
they then become double positive CD4+ CD8+ then in later stage become either CD4+ or CD8+ |
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what is the first step in the development of TCR sequence
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in cells that are double negative CD4- and CD8- the variable segments of TCR beta chain undergo rearrangement
Beta chain associates w/ pre alpha chain + CD3 if Beta chain that is being tested out is active the beta-alpha CD3 comples will start to send signals |
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what does a pre alpha chain do
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used to try out the newly rearranged beta chain
pre alpha is always working and will associate with the new beta chain and CD3 forming a signaling complex on the cell surface which starts to send signals |
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if the new beta chain being tested out works and sends signals what happens to the cell
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Qthe cell will survive
it will become double positive CD4+ and CD8+ will be expressed on the surface rearrangment of additional Beta cells will be suppressed rearrangment of variable alpha chain genes if rearrangement of alpha chain is successful a mature TCR is formed if beta chain or alpha chain rearrangment is unsuccessful the T cell dies |
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why is rearrangment of further beta chains suppressed after an active beta chain has been found
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this is allelic exclusion and done because the T cell wants to express only one Beta chain so once it has made a successful one the rest are inhibited
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when does the T cell send signals
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when the Beta-pre alpha complex is formed and after alpha gene rearrangment
if alpha chain rerrangment works the alpha chain combines with the beta chain and continues to send signals |
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what is the purpose of positive selection for self MHC restriction
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you want to only have TCR that recognize/bind to our MHC b/c TCR/MHC interaction is limited only to our MHC of our own genotype
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what performs the positive selection for MHC restriction and how
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cortical epithelial cells they have both MHC1 and MHC2
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MHC1 binds what
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CD8
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MHC2 binds what
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CD4
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what occurs in positive selection for self MHC restriction
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dbl positive cells are subjected to positive selection
you want low affinity to MHC (cell will survive) don't want too high of an affinity for TCR to MHC because it may lead to autoimmunity if no affinity btwn TCR and MHC the T cell dies Progression to single positive TCR binds MHC1 = CD8 TCR binds MHC2 = CD4 |
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what stage of T cell ontogeny does a T cell progress to being single positive
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positive selection for MHC restriction
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what occurs in negative selection of T cell
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it removes any self reactive T cells, you want to remove any T cells that react to self antigens
conventional dendritic cells and macrophages present ubiquitous self antigens medullary thymic epithelial cells present tissue specific antigens (albumin made by liver) if TCR reacts w/ ubiquitos antigen or tissue specefic antigen the T cell dies |
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where does negative selection for T cells occur
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medulla
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what cells participate in negative T cell selections
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convetional dendritic cells
macrophages medullary epithelial cells |
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what are ubiquitos self antigens
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proteins present in every cell in your body
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what are the stages T cell tolerance
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central tolerance
peripheral tolerance |
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what is central tolerance
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removes self reactive T cells
occurs in thymus |
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what is peripheral tolerance
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occurs in lymph nodes and places T cells go (2ndary lymphoid tissue)
this is done because central tolerance isn't 100% effective and a few self reactive T cells leak out and peripheral tolerance removes them |
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what are the peripheral tolerance mechanisms
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activation of induced cell death
CTLA4 expression regulatory T cells lack of co stimulation by nonimmune system cells |
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what is meant by lack of costimulation by nonimmune system cells
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every cell in the body has MHC1 and is presenting its own self peptide and when they come in contact w/ cells of the immune system they're not expressing any costimulators (no B7)
these non immune cells aren't capable of stimulating our immune system b/c no costimulatior B7 no costimulation causes: anergy and death of the T cell |
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what is involved in T cell tolerance
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dendritic cells will not make B7 if there is no danger and T cell anergy results if DC tries to present antigen w/o B7
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what occurs in the 1st 3 stages of B cell speceficity
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stage 1
rearange D and J segments of Ig heavy chain (D-J joins) stage 2 V-DJ join on one chromosome if 1st rearrangement is non productive the other chromosome rearranges if 2nd chromosome is non productive then cell dies stage 3 V-DJ combimes with MU heavy chain (to test it out) which joins with pseudo light chain (temporary light chain) to form SURRUGATE IgM (sIgM) sIgM goes to the surface and forms a signaling complex with IgALPHA and IgBETA and begins to send signals step 4 signals from sIgM provide allelic exclusion of any heavy chain rearrangment of any more V-DJ segments ALLELIC EXCLUSION stage 5 sIgM signal light chain genes to undergo rearrangement since we already have a successful heavy chain gene so want light chain to pair it up *if rearrangement doesn't work cell dies IF REARRANGEMENT WORKS LIGHT AND HEAVY CHAINS FORM SURFACE IgM stage 6 sIgM signals all other light chains to stop rearrangement (allelic exclusion) virgin mature naive B cells go to 2ndary lymphoid tissue ready for antigen contact |
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what is a marker for stage 6 of B cell development
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IgD expression
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what is the mechanism for B cell tolerance
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B cells that get activated by self antigen in the marrow undergo apoptosis (clonal deletion)
some B cells have surface Ig that recognize self antigen but don't get activated and anergy occurs and they die Ignorance may occur - B cell recognizing self antigen never encounters the antigen in the periphery |
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what is needed for NK cell development
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IL-2 (IL2 and IL2 receptor are both expressed by NK cells)
IL-15 |
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what do NK cells produce
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IFN GAMMA
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what surface proteins does NK cells have
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CD56 FcGAMMARIII
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what antibodies do neonate have
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maternal IgG
HL = 30 days |
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when do neonates get vaccinated
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depending on the [IgG]
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