Immune System - Lecture 3 Part A Flashcards
What is the Adaptive immune response composed of?
- Humoral/antibody mediated response
* Cell mediated immune response
What type of WBCs are involved in the Humoral Adaptive response?
B lymphocytes
What type of WBCs are involved in the Cell mediated adaptive response?
T lymphocytes
What type of lymphocytes are involved in the adaptive immune response?
T and B lymphocytes
What is the general role of B cells in the adaptive response?
Their main function is to get rid of soluble or free toxins, viruses and bacteria
What is the general role of T cells in the adaptive response?
Monitor the status of ourselves for signs of viral infection, tumors and foreign proteins after phagocytosis
Where are T cell produced?
In the bone marrow
Where do T cells finish their development and become mature?
In the Thymus
What do T cells express to recognize antigens?
Receptors called T cell receptors or TCR
What do TCRs do for T cells?
Allow them to recognize antigens
What are TCRs composed of?
A U-shaped variable domain and a constant domain which is the bottom part
What is the function of the variable domains of TCRs?
They bind to the antigen
What is unique about the variable domain of TCRs?
They are susceptible to DNA recombination which allows for different specificities of antigens to be recognized
What is the function of the Constant domain of TCRs?
It lifts the receptor away from the membrane of the T lymphocyte allowing it to reach antigens
What do TCR receptors recognize?
Both the MHC molecule and the peptide antigen that is displayed by the MHC molecule
What additional receptors do mature T cells have?
Coreceptors
What are the additional receptors on mature T-cells involved in?
Antigen recognition
What are the two types of co-receptors on T lymphocytes?
CD4 and CD8
What do the coreceptors on T lymphocytes do?
Recognize MHC molecules and are required for T cell activation
Which T lymphocyte co-receptor recognizes MHC II?
CD4
Which T lymphocyte co-receptor recognizes MHC I?
CD8
What do early T cells lack?
Co-receptors
What are Double Negative cells?
Early T cells that lack co receptors
When do T cells develop co-receptors?
During their development
What happens if an early T cell failed to express the TCR receptor?
The cell will die
What happens to the developing T cells that are able to produce the TCR receptors?
They will go on to produce both CD8 and CD4 co-receptors
What are Double Positive T cells?
T cells that have both the CD4 and CD8 receptors
What occurs after T cell have both CD8 and CD4 coreceptors?
They undergo a selection process to become single positive cells and a second selection process to become mature naive T cells
What does the second selection process that developing T cells undergo ensure?
That cells that are autoreactive are eliminated from the body
What is the only form that T cells can recognize antigens?
T cells can recognize antigens on antigen presenting cells that are bound the MHC molecules but not on pathogens themselves
What crucial role to antigen presenting cells have in the adaptive response?
They activate T cells by presenting antigens to them
What three signals are required for T cell activation?
- TCR receptors must recognize the MCH and the represented peptide and the coreceptors must recognize it as well
- Costimulatory molecules on the T cell must interact with the antigen
- Cytokines to direct differentiation into effector cells
When activating T cells what is the purpose of the costimulatory signal in order to activate it?
The costimulatory molecules increase the interaction between the two cells because just the binding to MHC has low affinity to prevent autoreactive cells
What is the purpose of cytokines in T cell activation?
They direct cell differentiation into effector cells
Why is Interleukin II an important cytokine for T cells?
It stimulates the proliferation of T cells resulting in an increased number of effector cells to help fight infection
What occurs in T cell activation if the Costimulatory signal doesn’t occur?
Anergy occurs and the T cell is unresponsive and not activated so it does not secrete cytokines or proliferate
Why is Costimualtion important to activate T cells?
It prevents an unnecessary immune response
Which type of T lymphocytes require an extra type of activation?
Those containing CD8 coreceptors
What do T lymphocytes with CD8 receptors need in order to become fully activated?
Costimulation by T helper cells or CD4 cells
What are the two ways that CD8 T cells can become fully activated?
- Sequential stimulation
* Simultaneous stimulation
What is the other name for CD8 T cells?
Cytotoxic T cells
Why do CD8/ Cytotoxic T cells need an addition signal for activation?
Because T Cytotoxic cells are really harmful to the host especially when activated unnecessarily
What is another name for CD4 T cells?
Helper T cells
How does sequential stimulation CD8 cells work?
The T help cell will first engage with the antigen producing cell (licensing it) and enhance its ability to engage with the CD8 cell. Then the T cytotoxic cell will be activated by the antigen presenting cell when it binds to it
How does Simultaneous stimulation of CD8 cells work?
The CD4 (T helper cell) and the CD8 cell both engage at the same time with the antigen presenting cell and exchange signal allowing he antigen presenting cell to activate the CD8 cell
How does the secretion of cytokines after activation of T cells affect the T cells?
Cytokines stimulate the activation and proliferation of T cells resulting in an increased number of antigen specific lymphocytes
What is Clonal Expasnion?
The increased proliferation of T cells after the release of cytokines resulting in antigen specific T cells facilitating elimination
When are memory cells alive?
Memory cells are alive always and circulate through the body waitin for a second exposure
When do memory cells respond with higher reactivity to an infection?
When there is a subsequent exposure to an infection
