T cell biology Flashcards
Which multipotent cell creates T cells, B cells, NK cells
Common lymphoid progenitor
Where do T cells go to mature
Thymus
What are the transcription factors that activate T cell genes
Notch1, GATA3
Where does the maturation for T cells start in the thymus
Cortex
In the cortex what is cytokine that is required for early T cell development
IL-7
Where are the largest amount of mature T cells in the thymus
Medulla
What are the stages of T cell maturation, where are these locations
Pro-T (thymus), Pre-T (thymus), Double positive (thymus), Single positive/immature T cell (thymus), naive mature T cell (periphery)
What are the two types of polypeptide chains for the T cell receptor
Alpha Beta TCR, Gamma Sigma TCR
Which of the polypeptide chains of the TCR is least common, what is the percentage,where are they located
Gamma Sigma TCR, 1 to 10%, lungs, skin, gut
T/F:Both alpha beta and gamma sigma TCR bind MHC molecules
False: Gamma sigma TCR donot bind MHC complexs but instead bind phospholipds, phospho-antigens, and heat-shock proteins
What are the functions of gamma sigma TCRs
primarily innate immune response, respond rapidly to pathogens, lack memory response
T/F:Once committed to Alpha Beta the TCR cannot further rearrange to use gamma delta
True
What is the function of alpha beta TCR
Adaptive immune response binds (with assistance of co-receptors) to peptide displayed by MHC on antigen presenting cells, Respond within days, show memory response
What are the small linear fractions that actually interact Alpha Beta TCR
MHC1,MHC2, small antigen peptides
What makes up the TCR complex
TCR, (2)CD3, 2 Zeta chains
What is the function of CD3 and Zeta chains
Signal transduction
in Stage 1 (double negative) what is the stage of maturation, is there differentiation into one of the two types of TCR, what part ofthe TCR is present
Pro T cell, decision to become Alpha Beta or Gamma Sigma is made, only the Beta chain of the TCR is expressed
In Stage 2 (double positive) what is the stage of maturation, what are the transcription factors active and what do they do, what is other part of the TCR is expressed
Pre T cell, RAG1 and RAG2: trigger alpha rearrangement, alpha chain is expressed
At what stage is the CD4+ AND CD8+
Stage 2 (double positive)
T/F: The TCR complex, CD4+ and CD8+ are all present during Stage 2 (double positive)
True
What occurs during Stage 3
double positive T cells loses one of the CD chains, gains the function of their respective chain, migrate to the medulla while undergoing positive and negative selecton
What is the end result of Stage 3
Productive TCR complex and CD4+or CD8+/mature single positive T cell
What happens to a mature T cell
leaves medulla and circulates through the lymphatic system
What occurs in positive selection
immature double positive T cells encounter epithelial cells that displays self peptides on MHC1 or MHC2
T/F: In positive selection low avidity for self peptide MHC complexes promotes T cell survival, T cells that do not recognize self MHC die by apoptosis
True
What happens during the transition of positive selection
Double positive T cells that recognize MHC1 will lose CD4 chain and become CD8+ T cells, Double positive T cells that recognize MHC 2 will lose CD8 chain and become CD4+ T cells
What is the result of positive selection
Self-MHC restricted Single positive T cells
What occurs in negative selection
double positive or single positive cells encounter APCs that display self peptides bound to MHC Class 1 or 2
What will trigger apoptosis in negative selection
Strong recognition (high avidity) of self peptide slef MHC complex
What is the result of negative selection
Self tolerant T cells
What is the most common stage of T cell in the thymus
Double positive
What is the majority of T cells
CD4 “helper”
What is the function for CD4 T cells
Help B-lymphocytes develop into plasma cells, Help activate CD8+ T cells, Help macrophages effect delayed hypersensitivity reactions
CD4 T cell type: TH1
activate cytotoxic T lymphocytes and macrophages, initiate delayed hypersensitivity reaction
CD4 T cell type: TH2
activate B lymphocytes to become plasma cells=IgE production, Eosinophil activation
CD4 T cell type: TH17
Pro-inflammatory
CD4 T cell type: Treg
Suppress activity of T lymphocytes and B lymphocytes=self tolerance
T/F: The differences made between CD4 subtypes is by the surface marks
False: Differentiation made is based on signature cytokines secreted
What is the function of CD8 T cells
elimination of target cells
What does perforin do
Pokes holes in the cell membrane
What are the toxic cytokines that are released from CD8+
INF- gamma and INF-alpha
