Immunology - Final - Part 4

davidwurbel7's version from 2015-12-15 20:29

Ag Recognication

Question Answer
Chains are anchored in the plasma membrane, and are not produced in a secreted formTCRs
Do not undergo class switching or affinity maturation during the life of a T cell cloneTCRs
Has three hypervariable, or complementarity-determining regions (CDRs)TCRs
Like antibodies, CDR3 is the most variable among different TCRs and the 3-D structure is very similar to the Fab region of an Ig moleculeTCRs
T cells that are abundant in epitheliaGamma Delta TCRs
Approximately 5% to 10% of T cells in the body express these TCR receptors which are structurally similar to the αβ TCR but have very different specificitiesGamma Delta TCRs
A complex of proteins called the CD3 and ζ proteins is associated with the TCR, which together make up thisTCR Complex
A complex of proteins associated with the TCR, which together make up the TCR Complex, which deliver the activating signalCD3 and ζ
This is composed by one strand of epsilon gamma and one strand of epsilon deltaCD3
Additional activation signaling is required to activate a T cell is delivered byCD4 or CD8
These are the inhibitory signals found in NK cells that prevent the killing of healthy cellsITIMs
Pre-lymphocytes that fail to express antigen receptors die byApoptosis
This is based on expression of intact antigen receptor components and what they recognizeT Cell Selection
The first chain tested in B cellHeavy Chain
The first chain tested in T cellBeta Chain
Generating extremely diverse repertoires of B and T lymphocytes, and the generation of diverse receptors is intimately linked to the process ofLymphocyte Maturation
The expression of diverse antigen receptors is the central event inLymphocyte Maturation
Proliferation of Pro-T cells is dependent on thisIL-7
IL-7 is the dependent molecule for the proliferation of these cellsPro-T Cells
Proliferation of these cells is not dependent on IL-7Pro-B Cells
Immature T cells fails this selection because of strong MHC self antigen recognitionNegative Selection
Immature T cells fails this selection because of no MHC ecognition of self antigenPositive Selection
Immature T cells passes this selection because of weak MHC self antigen recognitionPositive Selection
Maintains and expands the number of T cell progenitors before they express antigen receptors, thus generating a large pool of cells in which diverse antigen receptors may be producedIL-7
The variable regions of the heavy chains and light chains are chosen byRandom Recombination
The expression of B and T lymphocyte antigen receptors is initiated by this process of gene segments that code for the variable regions of the receptors, and diversity is generated during this processSomatic Recombination
Only the Ig heavy chain and TCR β loci contain these segmentsDiversity (D) Gene Segments
All antigen receptor gene loci contain this segmentJoining (J) Gene Segment
The somatic recombination of V and J, or V, D, and J, gene segments is mediated by a group of enzymes collectively calledVDJ Recombinase
The lymphoid-specific component of the VDJ recombinase that recognizes DNA sequences that flank all antigen receptor V, D, and J gene segmentsRecombinase-Activating Gene (RAG)-1 and RAG-2
This is achieved through both combinatorial diversity and junctional diversityAntigen Receptors Diversity
Different combinations of V, D, and J gene segments in different clones of lymphocytesCombinatorial Diversity
Changes in nucleotide sequences introduced at the junctions of V, D, and J gene segmentsJunctional Diversity
May remove nucleotides from the edges of V, D, and J gene segments at the time of recombination resulting in recommended sequencesExonucleases
This lymphocyte-specific enzyme catalyzes the random addition of nucleotides at the V, D, and J gene segments at the time of recombinationTerminal Deoxyribo-Nucleotidyl Transferase (TdT)
The random addition of nucleotides that are not parts of germline genes to the sites of V(D)J recombination, forming so-calledNontemplate-Encoded (N) Regions
During an intermediate stage in the process of V(D)J recombination before breaks in the DNA are repaired, overhanging DNA sequences may be generated and then filled in by these which introduce even more variability at the sites of recombinationPalindromic (P) -Nucleotides
The maturation of B lymphocytes occurs mainly in theBone Marrow
Progenitors committed to the B cell lineage proliferate, giving rise to a large number of precursors of B cellsPro-B Cells
Ig genes in the heavy chain locus of one chromosome recombine and give rise to the μ heavy chain protein. Most of this protein remains in the cytoplasm, and cytoplasmic μ is the hallmarkPre-B Cells
Some of the μ protein is expressed on the cell surface in association with two other invariant proteins that together are called the surrogate light chain, because they resemble light chains and they associate with a heavy chain. The μ chain and surrogate light chain (VpreB and lambda5) associate with the Igα and Igβ signaling molecules to form thePre-B Cell Receptor (Pre-BCR) Complex
VpreB and lambda5 are the components of this which combines with the heavy chain in the first check point of B cellsSurrogate Light Chain
Combines with the TCR-β to form the Pre-B cell receptor complexPre-Tα
The μ chain and surrogate light chain (VpreB and lambda5) associate with the Igα and Igβ signaling molecules to form thePre-B Cell Receptor (pre-BCR) Complex
This is the first checkpointμ Chain Protein
Process shuts off recombination of Ig heavy chain genes on the second chromosome, because of which each B cell can express Ig from only one of the two inherited parental allelesAllelic Exclusion
Recombination at the Ig light chain locus, first kappa and then lambda. Whichever functional light chain is produced associates with the μ chain to form the completeMembrane-associated IgM Antigen Receptor
VpreB and Lambda5 are components ofSurrogate Light Chain
Cytoplasmic μ is the hallmark ofPre-B Cells
IgM-expressing B lymphocyte is theImmature B Cell
The final maturation step of B cells occurs because the recombined VDJ heavy chain RNA is alternatively spliced onto Cμ RNA or Cd RNA, giving rise to μ or d mRNACoexpression of IgD with IgM
An immature B cell binds a self antigen in the bone marrow with high affinity, further maturation is stoppedCheck Point 1 Negative Selection
Reactivation the V(D)J recombinase enzyme, generate a second light chain, and change the specificity of the antigen receptorReceptor Editing
The most immature progenitors are called pro-T cells or this because they do not express CD4 or CD8Double-Negative T Cells
T cells expand in number mainly under the influence of this chemical produced in the thymusIL-7
Some of the progeny of double-negative cells undergo TCR beta gene recombination (chromosome 7), mediated byV(D)J Recombinase
If successful VDJ recombination takes place on one chromosome and a β chain protein is synthesized, it is expressed on the surface in association with an invariant protein called pre-Tα, to formPre-TCR Complex
The surviving cells express both the CD4 and CD8 coreceptors, and these cells are calledDouble-Positive T cells
Double-Positive T cells are at this point in the maturation processImmature T Cells
Recognition an MHC molecule in the thymus (a self MHC molecule displaying a self peptide), that T cell is selected to survivePositive Selection
T cells whose TCRs recognize class I MHC-peptide complexes preserve the expression of CD8, the coreceptor that binds to class I MHC, and lose expression of CD4, the coreceptor specific for class II MHC moleculesCD8+ T Cell
T cell recognizes class II MHC-peptide complexes, that cell maintains expression of CD4 and loses expression of CD8CD4+ Helper T Cell
Immature, double-positive T cells whose receptors strongly recognize MHC-peptide complexes in the thymus undergo apoptosisCheck Point 2 Negative Selection