T-Cell Diversity Flashcards
(35 cards)
Define T-cells and where they are formed.
Lymphocytes that express T-cell antigen receptors (TCR’s); formed in the thymus.
What do T-cells secrete and what do these secretions control?
Cytokines: Induce changes in cells, especially the differentiation of B cells into Plasma cells… these secretions control –> Cytotoxins: (Kill [infected] cells via the adaptive immune response.)
What antibody is associated with B-cells, and with Plasma Cells?
B cell = IgM ; Plasma cell = IgG
What is the Immunologic Synapse? What secretion is it associated with?
Space that allows for communication between T-cell and Target cell; associated with cytotoxins.
Define DiGeorge Syndrome.
Lack of a thymus due to a mutation in the transcription factor causing T-cell deficiency. (Susceptible to viral/bacterial/fungal/parasitic infections.)
Why would the lack of T-cells cause susceptibility to viruses?
Because Cytotoxic T-cells kill virus infected cells and Helper T cells provide cytokines to B-cells that allow them to make neutralizing antibodies against viruses.
Why does lack of T-Cells cause susceptibility to Pygogenic (pus inducing) Bacteria? Intracellular Bacteria?
T-cells are essential for B-cell responses (to eliminate bacteria);
T-cells make cytokines (interferon-gamma) that activate macrophages to kill intracellular bacteria.
About how many different T-cells are there in Humans? TCR’s?
10^12 ; 10^10
Where does V(D)J recombination generating T cell diversity occur? How does this contrast to B cell diversity?
In the thymus only; B cells diversify in Bone Marrow and the Periphery in a process called Affinity Maturation.
Irreversible genomic rearrangement occurs where?
At the alpha & beta loci (each lymph gets a unique Ab receptor).
What exactly are the alpha and beta loci?
They are each arm of the dimer receptor.
When does diversity of T-cell receptors occur, before or after encountering antigens?
Before, so your body is ready.
List the mechanisms for generating TCR diversity.
Each TCR has 2 chains (products of V(D)J). Multiple variable domain exons. Multiple diversity/joining segments. Imprecision in the joining process (nucleotides added/deleted– N region diversity).
Which molecule transmits T-cell receptor signals?
CD3 - once TCR binds to Ag, this molecules signals cell to react
What antigens do T-cells see?
MHC molecules loaded with peptides.
What are MHC molecules?
Cell surface proteins encoded by a genomic locus known as the Major Histocompatibility Complex
What is another name for MHC molecules in humans?
Human Leukocyte Antigens (HLA molecules)
Which MHC class has only 1 membrane penetrating chain and is slightly smaller?
MHC class 1.
What peptides are presented by MHC molecules?
Short (8-17 AA) peptides that come from the degradation of self or foreign proteins.
Where are these peptides generated?
Either the cytosol or in the endocytic compartments that retrieve proteins from outside cells.
What is the only way a T-cell receptor recognizes anything?
When it encounters a MHC – Peptide complex (not individually).
MHC Class, CD4/CD8?
CD4 T-Cell: Class II
CD8 T-Cell: Class I
Type of T-Cell, CD4/CD8?
CD4 T-Cell: Helper T-Cell
CD8 T-Cell: Cytotoxic T-Cell
On which type of cells, CD4/CD8?
CD4 T-Cell: Dendritic/B/Macrophage
CD8 T-Cell: All nucleated cells
