Test 2: T cell Maturation and Activation Flashcards
What is the difference between the receptors of innate and adaptive immunity?
receptors of adaptive immunity are clonal
What do T cells recognize?
recognize peptides displayed by MHC molecules
What is the structure of T cell receptor?
membrane-bound heterodimeric protein composed of an alpha chain and beta chain with a variable and constant region
What is the binding site for MHC class I?
variable domains of alpha chains
What is the binding site for MHC class II?
variable domains of alpha and beta chains
In gremlin organization of T cell receptor gene location, what accounts for the diversity in gene segments?
somatic recombination
What is the recombination of TCR gene segments?
random selection of segments
What are the steps of mediation by lymphocyte specific VDJ recombinase that brings 2 segments close together?
- first step: recombination of D and J segments
- second step: recombination of V segments with fused D-J element
- third step: recombination of C segment fused V-D-J element
Which diversity of TCR is unlimited: combinatorial vs junctional?
junctional diversity has tremendous diversity
What does weak recognition of MHC+ peptide lead to?
selection of selected T cells that are single positive
What happens to both strong recognition and no recognition of MHC+ peptide?
lead to death
- strong recognition= negative selection
- no recognition= neglection
What happens with antigen recognition by T cells without costimulation?
induce unresponsiveness
What must happen for T cells to proliferate?
engagement of B7 on AP by CD28 on T cells that provide signal 2 and induce proliferation
What are inhibitory receptors for in activated T cells?
critical for limiting and terminating immune response
How are CD8 T cells activated?
concomitant activation of CD4 T cells provide help to CD8 T cells via IL-2 production which allow for proliferation and differentiation
How do T cells expand and contract?
antigen-specific T cell clones expand in response to antigen to provide a large pool of effector cell to fight infection
How do effector CD4 T cells develop?
naive T cells proliferate/differentiate once acting with antigen
What happens to the effector T cells that do not leave lymph nodes?
Tfh move in follicle to function as helping B cells
What is the function of CD4 helper T cells?
- activate phagocytes via IFNy production and CD40-CD40L
- activate B cells to produce Ig via cytokine production and CD40-CD40L
How do naive and effector T cells migrate?
combination of adhesion molecules and chemokine receptors allow for T cell movement
What promotes cell survival in maturation of thymocytes?
expression of pre-TCR and TCR
- cells that do not express functional receptors die
What is the difference between naive T cells and effector T cells in regards to their location?
naive T cells circulate from lymph node to lymph node in search of their antigens while effector T cells get migrated to antigen sites in tissues to get reactivated and carry their function
