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POSC 649 Farnell Immunology Exam 2 Material Study Guide
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POSC 649 Farnell ImmunologyExam 2 Material Study Guide
Proliferation - Answer massive expansion of pre-B and T lymphocytes—Il-7 is a key
cytokine
Tolerance to self antigens - Answer Specific selection process in T-cells
Acquisition of antigen receptor: - Answer surface Immunoglobulin for B-cells / TCR for
T-cells.
Acquisition of functional competence: - Answer surface marker expression and effector
function capabilities.
Thymic architecture - Answer Divided into lobes.
In humans, located in thoracic cavity near lungs/heart.
Birds have 7 lobes on each side of the neck.
Divided into lobules
How is a lobule divided? - Answer Into a cortex and medulla
Pre-T-cell migration to Thymus - Answer Progenitor cells arrive in the thymus at the
junction of the outer cortex and central medulla- cortico-medullary border.
Funtionally immature thymocytes, referred to as double-negative T-cells since they do
not express CD4 or CD8 at this point in maturation.
Proliferation in the Thymus - Answer Progressively migrate to the cortex where massive
IL-7 induced proliferation of pre-T cells occurs.
Where are the majority of maturation events for T cells? - Answer within the cortex.
Where is the first region where thymoctyes first express complete TCR? - Answer In the
Thymic Cortex.
What do Thymocytes mature into after expressing TCR in the Thymic cortex? - Answer
Mature into either CD4 or CD8 positive cells
Where do thymocytes/Tcells leave the Thymus? - Answer From the cortex they enter the
medulla and leave the thymus by either veins or lymphatics.
cortical epithelial cells - Answer Express MHC class 1 or 2 interacts with thymocytes
during positive selection which ever class interacts better determines differentiation
into CD4 or CD8 T cells.
,Look kind of like dendritic cells.
Thymic epithelial cells- simple speak - Answer regulate T cell development and function.
Also called Nurse cells.
Where are the dendritic cells located in the thymic epithelium? - Answer at the cortico
medullary border.
Thymic epithelial cells - Answer -have processes that form a cytoreticulum for cells to
attach to
-help form the blood-thymus barrier and the corticomedullary barrier
-form concentrically arranged clusters called Hassall corpuscles which secrete
cytokines
-don't have separate group of reticular fibers, has processes instead
Hassal's Corpuscles (Thymus) - Answer Found only in Thymus, discovered 1846 by
Arthur Hill Hassal.
Function is unsure but seems to have ties that benefit dendritic cells.
Produces Thymopoetin
nurse cells - Answer have long cytoplasmic processes that form deep invaginations in
the cortex.
This increases the surface area of the thymic cortex and forces lymphocytes to have
prolonged contact with the various cells and surface markers.
What must a thymocyte pass though to reach the medulla? - Answer Through the
invaginations in the thymic cortex produced by the nurse cells.
Surface Molecules Expressed by Non-lymphoid Thymic Cell: MHC Class I (MHC I) -
Answer medullary macrophages
Surface Molecules Expressed by Non-lymphoid Thymic Cell: MHC Class II (MHC II) -
Answer cortical epithelial cells, cortical DC's and Medullary.
Surface Molecules Expressed by Non-lymphoid Thymic Cell: - MHC I and II: MHC I and II -
Answer Medullary DC's and medullary ep. Cells
Soluble Factors produced by non lympoid Thymic cells: What hormones/cytokines do
Thymic epithelial cells secrete? - Answer Il-7
Thymosin
Thymulin
,Thymopoetin
TCR - Answer T cell antigen receptor
What are the two types of TCR? - Answer Alpha and Beta in humans, (~90% of T cell
repertoire))
Gamma and Delta dominate in birds.
What is the first necessary step to lymphocyte "growing up" to full functioning
T-lymphocyte? - Answer TCR maturation and expression
What is TCR coordinated with? - Answer Coordinately regulated with expression of CD3
CD4 and CD8
What is the first form to be expressed? - Answer gamma delta TCR is the first form to b
expressed
What overtakes gdTCR? - Answer Alpha Beta TCR expression overtakes gd TCR
expression
GALT - Answer Gus associated Lymphoid Tissue (ie, ceca)
What tissue in adult chickens has the greatest number of gammadelta expressing T
cells? - Answer GALT
Approximately how many thymocytes die during the process? - Answer 95-98%
What characteristics do surviving T cells have? - Answer Recognize foreign antigens,
tolerant to self antigen, posses necessary surface markers to carry out effector
functions.
What are the 3 stages to expression on thymocytes? - Answer 1. Early Stage
2. Double Positive Stage
3. Final Stage
Early Stage - Answer no expression of either CD4 or CD8— double negative cells
Double Positive stage - Answer T-cells express CD4 and CD8 at the same time
Final Stage - Answer T-cells express either CD4 or CD8.
CD4 and CD8 Expression sequence - Answer CD4- / CD8-
CD4+ / CD8+
CD4+ / CD8-
CD4- / CD8+
, Two types of thymic selection processes - Answer 1. Positive selection-generation of
MHC restriction
2. Negative selection-generation of self tolerance.
MHC restriction - Answer Co-recognition, Need specific peptide and MHC molecule in
order for the T cell to recongize it.
the property that a given T-cell receptor recognizes its peptide antigen only when the
peptide is bound to a particular form of MHC molecule.
the requirement that immune cells share the same MHC or "self" antigens in order to
interact and immunologically respond together
What is responsible for MHC restriction? - Answer Positive selection
Positive selection and MHC restriction: CD4 and CD8 cells - Answer - CD4 cells are MHC
II restricted - CD8 cells are MHC I restricted
What is the goal of positive selection? - Answer is for T-cells to recognize peptide
antigens only when associated with "self" MHC molecules
Mechanism for positive selection - Answer both CD4 and CD8 cells which recognize
"self" antigens associated with either MHC II or MHC I, respectively, with LOW AVIDITY
are rescued from PCD (apoptosis).
Difference between Negative and positive selection - Answer Negative selection is
basically tolerant.
Positive selection recognizes self antigens.
Negative selection: - Answer describes the generation of "self tolerance" in developing
T-cells.
In what process are self reactive clones deleted? - Answer Negative selection
What is the primary function in Negative selection and self tolerance? - Answer At this
stage in the selection process, T-cells are presented "self" peptides in "self MHC"
molecules. Those T-cells that react by binding with high avidity to self-peptides
(antigens) when associated with self-MHC molecules are negatively selected—i.e. they
are deleted by apoptosis / PCD.
If they overreact, they die. :)
What T-cells would be removed from development in the THymus by apoptosis or PCD? -
Answer T-cells not expressing/possessing appropriate or functional surface markers.
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