PCB 3233 Exam 4 Study Guide Questions With Correct
// // // // // // // //
Answers
//
start //of //chapter //7
Where //does //T-cell //maturation //take //place? //- //CORRECT //ANSWERS(S)✔✔T-cell //maturation
//takes //place //in //the //thymus
Be //able //to //understand //some //similarities //and //differences //between //B //cell //and //T //cell
//development.
a. //Examples: //Where //do //they //derive? //What //cellular //mechanisms //or //processes //are //shared
//between //the //two? //What //comprises //their //cell //lineages? //- //CORRECT //ANSWERS(S)✔✔Both
//B-cells //and //T-cells //derive //from //the //bone //marrow //stem //cells //but //the //T-cell //moves //to
//the //thymus //to //mature //while //the //B-cell //stays //in //the //bone //marrow. //Both //undergo //gene
//rearrangement //which //produces //antigen //receptors. //T //cells //have //two //lineages.
Regarding //the //initial //stages //of //T-cell //maturation, //explain //the //direction //of //its //migration
//using //"subcapsular //region", //"medulla", //and //"cortex" //as //references //in //your //description.
//Where //would //you //expect //to //find //macrophages? //What //about //dendritic //cells? //- //CORRECT
//ANSWERS(S)✔✔As //the //T-cell //matures, //it //migrates //from //the //subcapsular //region //of //the
//thymus //to //the //inner //cortex //and //to //the //medulla. //Macrophages //are //found //in //both //the
//cortex //and //the //medulla. //Dendritic //cells //are //found //in //the //medulla.
In //the //thymus, //what //is //the //role //of //macrophages? //Where //are //Hassal's //corpuscles //found?
- CORRECT //ANSWERS(S)✔✔Macrophages //remove //the //thymocytes //that //do //not //mature
// //
//properly. //Hassal's //corpuscles //is //found //in //the //medulla //of //the //thymus //and //it //induces //the
//development //of //regulatory //T //cells.
Evident //from //patient's //who //demonstrate //DiGeorge's //syndrome, //the //development //of //a
//functional //T-cell //repertoire //is //crucial //to //an //individual's //health. //What //causes //DiGeorge's
,//syndrome? //Know //the //chromosome //affected. //Identify //what //is //NOT //being //produced //in
//this //clinical //condition, //and //what //further //consequences //are //associated. //Can //DiGeorge's
//syndrome //be //cured? //- //CORRECT //ANSWERS(S)✔✔DiGeorge's //syndrome //is //caused //by //a
//deletion //in //chromosome //22 //where //the //thymus //fails //to //develop //and //T //cells //are //absent.
//The //lack //of //T //cells //and //thymus //increases //susceptibility //to //a //wide //range //of
//opportunistic //infections //and //it //resembles //SCID //(severe //combined //immunodeficiency
//disease). //Cannot //be //cured.
The //thymus //is //considered //to //be //completely //developed //before //birth. //However, //its
//deterioration //results //with //natural //aging, //indicating //that //the //younger //you //are, //the //more
//active //it //is. //Knowing //this, //would //you //expect //T-cell //immunity //to //become //defective
//overtime? //Why //or //why //not? //What //about //in //the //case //of //a //thymectomy //(removal //of
//thymus); //would //you //expect //impairment //then? //- //CORRECT //ANSWERS(S)✔✔T-cell
//immunity //does //not //become //defective //over //age. //The //thymus //just //does //not //develop //as
//many //T-cells //over //time. //T-cells //stay //in //circulation //for //several //years. //T-cells //do //not
//become //defective //even //after //a //thymectomy.
How //does //the //life //of //a //T //cell //differ //from //that //of //a //B //cell? //Which //lives //longer //and //why
//do //you //think //that //is? //(Hint: //understand //what //"self //renewing" //means //in //this //context) //-
//CORRECT //ANSWERS(S)✔✔T //cells //are //long-lived //and //self-renewing. //T //cells //are //in
//circulation //in //the //blood //stream //for //several //months. //Self-renewing //cells //divide //to
//maintain //the //amount //of //cells.
Double-Negative //(DN) //thymocytes //vs. //Double-Positive //(DP) //thymocytes:
a. //When/why //are //they //called //DN //thymocytes?
i) //What //cell-surface //proteins //are //expressed? //Which //are //NOT //being //expressed?
ii) //What //is //the //importance //of //Notch //1 //for //these //thymocytes?
b. //When/why //are //they //called //DP //thymocytes?
i) //What //cell-surface //proteins //are //being //expressed //at //this //point? //- //CORRECT
//ANSWERS(S)✔✔a. //T //cells //that //express //the //αβ //TCR //but //do //not //express //CD4/CD8/NK //cell
//markers. //This //happens //when //the //progenitor //T //cell //expresses //T-cell //specific //adhesion
//molecule //CD2 //and //other //molecules //but //not //TCR //complex.
, i) //CD2 //and //CD5 //are //expressed. //CD4 //and //CD8 //are //not //expressed.
ii) //Notch //1 //keeps //the //T-cell //on //the //T-cell //path.
b. //T //cells //that //express //both //CD4 //and //CD8.
i) //CD2, //CD5, //CD4, //and //CD8 //are //being //expressed.
The //two //T-cell //lineages: //α:β //and //γ:δ
a. //Which //is //considered //to //be //the //majority //and //which //is //the //minority?
b. //Do //the //loci //lineages //derive //from //a //common //DN //or //DP //thymocyte //precursor?
c. //Which //loci //(α, //β, //γ, //δ) //begin //their //rearrangement //roughly //at //the //same //time?
i) //Understand //what //is //meant //by //"competition" //that's //observed //at //this //point, //and //what
//will //be //produced //as //an //outcome. //(Hint: //depends //on //what //T-cell //lineage //is //made, //think
//about //what //the //result //would //be //if //a //β //chain //was //made //before //γδ; //what //is //more
//frequent //outcome? //- //CORRECT //ANSWERS(S)✔✔a. //α:β //is //the //majority //and //γ:δ //is //the
//minority.
b. //Both //α:β //and //γ:δ //derive //from //double //negative //thymocyte //precursor.
c. //α, //γ, //and //δ //rearrange //at //about //the //same //time.
i) //"Competition" //means //that //depending //on //which //loci //begins //their //rearrangement //first,
//a //particular //lineage //will //arise.
Using //question //9 //as //a //guide, //be //able //to //understand //the //following //concepts //and
//potential //questions //that //can //be //associated //with //them:
a. //What //gene //segments //are //rearranged //for //the //alpha //and //beta //chains?
b. //How //many //attempts //can //be //performed //at //the //β-chain //locus //in //order //to //achieve //a
//productive //rearrangement? //Does //the //α-chain //locus //observe //more //attempts?
c. //Are //the //RAG //genes //used? //Is //the //12/23 //rule //observed? //- //CORRECT //ANSWERS(S)✔✔a.
//Alpha //chain //has //two //gene //segments //(V //and //J). //Beta //chain //has //three //gene //segments
//(V, //D, //and //J).
b. //β-chain //locus //has //up //to //4 //attempts //per //cell. //α-chain //locus //observes //more //attempts
//due //to //the //increase //presence //of //V //and //J //gene //segments.
// // // // // // // //
Answers
//
start //of //chapter //7
Where //does //T-cell //maturation //take //place? //- //CORRECT //ANSWERS(S)✔✔T-cell //maturation
//takes //place //in //the //thymus
Be //able //to //understand //some //similarities //and //differences //between //B //cell //and //T //cell
//development.
a. //Examples: //Where //do //they //derive? //What //cellular //mechanisms //or //processes //are //shared
//between //the //two? //What //comprises //their //cell //lineages? //- //CORRECT //ANSWERS(S)✔✔Both
//B-cells //and //T-cells //derive //from //the //bone //marrow //stem //cells //but //the //T-cell //moves //to
//the //thymus //to //mature //while //the //B-cell //stays //in //the //bone //marrow. //Both //undergo //gene
//rearrangement //which //produces //antigen //receptors. //T //cells //have //two //lineages.
Regarding //the //initial //stages //of //T-cell //maturation, //explain //the //direction //of //its //migration
//using //"subcapsular //region", //"medulla", //and //"cortex" //as //references //in //your //description.
//Where //would //you //expect //to //find //macrophages? //What //about //dendritic //cells? //- //CORRECT
//ANSWERS(S)✔✔As //the //T-cell //matures, //it //migrates //from //the //subcapsular //region //of //the
//thymus //to //the //inner //cortex //and //to //the //medulla. //Macrophages //are //found //in //both //the
//cortex //and //the //medulla. //Dendritic //cells //are //found //in //the //medulla.
In //the //thymus, //what //is //the //role //of //macrophages? //Where //are //Hassal's //corpuscles //found?
- CORRECT //ANSWERS(S)✔✔Macrophages //remove //the //thymocytes //that //do //not //mature
// //
//properly. //Hassal's //corpuscles //is //found //in //the //medulla //of //the //thymus //and //it //induces //the
//development //of //regulatory //T //cells.
Evident //from //patient's //who //demonstrate //DiGeorge's //syndrome, //the //development //of //a
//functional //T-cell //repertoire //is //crucial //to //an //individual's //health. //What //causes //DiGeorge's
,//syndrome? //Know //the //chromosome //affected. //Identify //what //is //NOT //being //produced //in
//this //clinical //condition, //and //what //further //consequences //are //associated. //Can //DiGeorge's
//syndrome //be //cured? //- //CORRECT //ANSWERS(S)✔✔DiGeorge's //syndrome //is //caused //by //a
//deletion //in //chromosome //22 //where //the //thymus //fails //to //develop //and //T //cells //are //absent.
//The //lack //of //T //cells //and //thymus //increases //susceptibility //to //a //wide //range //of
//opportunistic //infections //and //it //resembles //SCID //(severe //combined //immunodeficiency
//disease). //Cannot //be //cured.
The //thymus //is //considered //to //be //completely //developed //before //birth. //However, //its
//deterioration //results //with //natural //aging, //indicating //that //the //younger //you //are, //the //more
//active //it //is. //Knowing //this, //would //you //expect //T-cell //immunity //to //become //defective
//overtime? //Why //or //why //not? //What //about //in //the //case //of //a //thymectomy //(removal //of
//thymus); //would //you //expect //impairment //then? //- //CORRECT //ANSWERS(S)✔✔T-cell
//immunity //does //not //become //defective //over //age. //The //thymus //just //does //not //develop //as
//many //T-cells //over //time. //T-cells //stay //in //circulation //for //several //years. //T-cells //do //not
//become //defective //even //after //a //thymectomy.
How //does //the //life //of //a //T //cell //differ //from //that //of //a //B //cell? //Which //lives //longer //and //why
//do //you //think //that //is? //(Hint: //understand //what //"self //renewing" //means //in //this //context) //-
//CORRECT //ANSWERS(S)✔✔T //cells //are //long-lived //and //self-renewing. //T //cells //are //in
//circulation //in //the //blood //stream //for //several //months. //Self-renewing //cells //divide //to
//maintain //the //amount //of //cells.
Double-Negative //(DN) //thymocytes //vs. //Double-Positive //(DP) //thymocytes:
a. //When/why //are //they //called //DN //thymocytes?
i) //What //cell-surface //proteins //are //expressed? //Which //are //NOT //being //expressed?
ii) //What //is //the //importance //of //Notch //1 //for //these //thymocytes?
b. //When/why //are //they //called //DP //thymocytes?
i) //What //cell-surface //proteins //are //being //expressed //at //this //point? //- //CORRECT
//ANSWERS(S)✔✔a. //T //cells //that //express //the //αβ //TCR //but //do //not //express //CD4/CD8/NK //cell
//markers. //This //happens //when //the //progenitor //T //cell //expresses //T-cell //specific //adhesion
//molecule //CD2 //and //other //molecules //but //not //TCR //complex.
, i) //CD2 //and //CD5 //are //expressed. //CD4 //and //CD8 //are //not //expressed.
ii) //Notch //1 //keeps //the //T-cell //on //the //T-cell //path.
b. //T //cells //that //express //both //CD4 //and //CD8.
i) //CD2, //CD5, //CD4, //and //CD8 //are //being //expressed.
The //two //T-cell //lineages: //α:β //and //γ:δ
a. //Which //is //considered //to //be //the //majority //and //which //is //the //minority?
b. //Do //the //loci //lineages //derive //from //a //common //DN //or //DP //thymocyte //precursor?
c. //Which //loci //(α, //β, //γ, //δ) //begin //their //rearrangement //roughly //at //the //same //time?
i) //Understand //what //is //meant //by //"competition" //that's //observed //at //this //point, //and //what
//will //be //produced //as //an //outcome. //(Hint: //depends //on //what //T-cell //lineage //is //made, //think
//about //what //the //result //would //be //if //a //β //chain //was //made //before //γδ; //what //is //more
//frequent //outcome? //- //CORRECT //ANSWERS(S)✔✔a. //α:β //is //the //majority //and //γ:δ //is //the
//minority.
b. //Both //α:β //and //γ:δ //derive //from //double //negative //thymocyte //precursor.
c. //α, //γ, //and //δ //rearrange //at //about //the //same //time.
i) //"Competition" //means //that //depending //on //which //loci //begins //their //rearrangement //first,
//a //particular //lineage //will //arise.
Using //question //9 //as //a //guide, //be //able //to //understand //the //following //concepts //and
//potential //questions //that //can //be //associated //with //them:
a. //What //gene //segments //are //rearranged //for //the //alpha //and //beta //chains?
b. //How //many //attempts //can //be //performed //at //the //β-chain //locus //in //order //to //achieve //a
//productive //rearrangement? //Does //the //α-chain //locus //observe //more //attempts?
c. //Are //the //RAG //genes //used? //Is //the //12/23 //rule //observed? //- //CORRECT //ANSWERS(S)✔✔a.
//Alpha //chain //has //two //gene //segments //(V //and //J). //Beta //chain //has //three //gene //segments
//(V, //D, //and //J).
b. //β-chain //locus //has //up //to //4 //attempts //per //cell. //α-chain //locus //observes //more //attempts
//due //to //the //increase //presence //of //V //and //J //gene //segments.
