C5 - LESSON 2B: STAGES OF T CELL DIFFERENTIATION Flashcards
– site of differentiation
Thymus
– Lymphocyte Precursors
Thymocytes
– Chemical messenger that dictates migration of thymocyte
Chemokines
Early Surface markers of Thymocytes:
CD44 and CD25
Maturation period:
3 weeks
Early thymocyte
Double Negative Stage
Lacks CD4 and CD8
Double Negative Stage
Active Proliferation
Double Negative Stage
Outer cortex
Double Negative Stage
Influenced by Inteleukin-7
Double Negative Stage
Antigen receptors
TCR, CD3, a-chain and b-chain
Double Negative Stage
Contains both CD4 and CD8 markers
Double Positive Stage
Expression of CD3ab Receptor Complex
Double Positive Stage
Double positive cells with functioning TCR
Positive selection
Deletion of developing T cells
Negative Selection
Survivors of selection exhibit only one type of marker, either CD4 or CD8, and they migrate to the medulla.
Mature T Cells
MHC Class II Protein
CD4+ T Cells
Known as Helper or Inducer T Cells
CD4+ T Cells
TH1 – IFN-y and TNF-b
CD4+ T Cells
TH2 – IL-4, IL-5, IL-10 and IL11
CD4+ T Cells
MHC Class I Protein
CD8+ T Cells
Cytotoxic T Cells
CD8+ T Cells
Characterized by polyribosome filled cytoplasm
Antigen activation
Express receptors for IL-2
Antigen activation
Antigen activation Activities:
Assisting B Cells in Antibody production
Kills tumor and other target cells
Rejects grafts
Stimulates hematopoiesis in the bone marrow
Stimulates delayed hypersensitivity reaction
Larger than T and B Cells (15um in diameter)
Ability to mediate cytolytic reactions and kill target cells without prior exposure
Early defenders-lacks specificity
Surface Markers: CD56 and CD16
They play an important role as a transitional cell bridging the innate and the acquired response to pathogens
Gives time for T and B cells to activate
Two subsets of NK cells
High level of CD56 and low or no CD16
CD56 and high levels of CD16
Reduce more cytokines and help support antibody production
High level of CD56 and low or no CD16
Have a higher cytotoxic activity
CD56 and high levels of CD16
Develop in the thymus
T CELLS
Found in blood (60-80% of circulating lymphocytes), thoracic duct fluid, lymph nodes
T CELLS
Identified by rosette formation with SRBC’s
T CELLS
End products of activation are cytokines
T CELLS
Antigens include CD2, CD3, CD4, and CD8
T CELLS
Located in paracortical region of lymph nodes
T CELLS
Develop in the bone marrow
B CELLS
Found in bone marrow, spleen, lymph nodes
B CELLS
Identified by surface immunoglobulin
B CELLS
End product of activation is antibody
B CELLS
Antigens include CD19, CD20, CD21, CD40, MHC Class II
B CELLS
Located in cortical region of lymph nodes
B CELLS
arise in the bone marrow from hematopoietic stem cells.
Undifferentiated lymphocytes
They mature in the primary lymphoid organs.
Undifferentiated lymphocytes
For B cells, this takes place in the (?), while T cells acquire their specificity in the (?).
bone marrow
thymus
B and T cells can be recognized by the presence of surface antigens, or CDs, that are detected by (?).
monoclonal antibodies
B cell markers include (?).
CD19, MHC class II proteins, and surface immunoglobulins
The (?) act as receptors for antigen.
surface immunoglobulins
allow B cells to interact with T helper cells in the production of antibody
MHC class II proteins
When contact with specific antigen occurs, (?) differentiate into plasma cells, which produce antibody.
B cells
In the process, (?) are also created.
memory cells
These can rapidly respond the next time that same antigen is seen.
memory cells
Production of antibody is known as (?).
humoral immunity
T cells are distinguished by the presence of (?).
CD3, CD2, and either CD4 or CD8
is the receptor that interacts with sheep red blood cells to form rosettes, a simple test for the enumeration of T cells
CD2
Cells that express CD4 belong to a T-cell subset that includes (?), while CD8-carrying T cells are (?).
helper/inducer cells
cytotoxic/suppressor cells
The (?) serves as the receptor for antigen.
CD3 marker
The major portion of it is common to all T cells, but two chains—(?)—contain variable regions that can bind to only certain antigens.
alpha and beta
(?) go through a positive and then a negative selection process, whereby the surviving cells recognize MHC determinants along with foreign antigen.
T cells
The T cells are responsible for (?), which involves production of cytokines that serve as regulatory factors for the immune response.
cell-mediated immunity
A third class of lymphocytes, known as (?), are found in the peripheral blood and represent 5 to 15 percent of the total lymphocyte population.
NK cells
These are larger and contain more cytoplasm and granules than T or B cells.
NK cells
They are responsible for killing target cells, including those that are virally infected or cancerous, without previous exposure or sensitization to them.
NK cells
They do this by recognizing missing self-MHC antigens, in addition to detecting the presence of stress proteins on infected and cancerous cells.
NK cells
This is an important first line of defense against invasion by such cells.
NK cells
The Laboratory determination of individual lymphocyte populations is essential in diagnosis of such conditions as (?).
lymphomas, immunodeficiency diseases, unexplained infections, or acquired immune diseases such as AIDS
are identified using monoclonal antibodies directed against specific surface antigens.
Lymphocytes
They are enumerated through the use of (?), which categorizes cells on the basis of light scattering.
cell flow cytometry
eliminate subjectivity and are more precise, although more costly.
Automated methods
