Cell Mediated Immunity Flashcards
Where do T cells originate and mature?
- Originate from bone marrow
- Mature in the thymus
What is the key function of T cells in immunity?
Recognising and responding to antigens via MHC presentation
What does MHC restriction mean?
T cells can only recognise antigenic peptides presented on MHC molecules
Which MHC class presents to CD8+ T cells?
MHC I
Where can MHC I be found and what does it present?
On all nucleated cells and presents endogenous antigens
Which MHC class presents to CD4+ T cells?
MHC II
Where can MHC II be found and what does it present?
On antigen presenting cells and presents exogenous antigens
What is the function of CD8+ T cells?
Kill virus-infected or abnormal cells using perforin and granzymes
What is the function of CD4+ T cells?
Secrete cytokines to stimulate immune cells like B cells and macrophages
What is the function of regulatory T cells?
- Suppress immune responses
- Prevent autoimmunity
- Promote oral tolerance
What is the function of memory T cells?
Long lived cells that provide faster responses upon re-exposure to antigen
Which antigen presenting cell is most effective at activating naive T cells?
Dendritic cells
What are the three signal required for T cell activation?
- T cell receptor binds to MHC
- Co stimulatory signal
- Cytokines
What are two examples of co-stimulatory signals?
- CD28-CD80/86
- CD40-CD40L
What happens after T cells are activated?
- Clonal expansion
- Differentiation into effector and memory t cells
What is the structure of the TCR?
- Variable region - binds antigen
- Constant region - anchors receptor to the cell
What type of antigens do T cells recognise?
Processed protein fragments presented on MHC molecules
What cytokines are secreted by Th1 cells?
IFN-γ
What does IFN-γ promote?
Cell mediated immunity
What cytokines are secreted by Th2 cells?
- IL-4
- IL-5
- IL-13
What does the cytokines secreted by Th2 cells promote?
Humoral immunity especially IgE production
What cytokines are secreted by Th17 cells?
IL-17
What does IL-17 promote?
Inflammation and neutrophil recruitment
What is positive selection in the thymus?
T cells are selected for their ability to recognise self MHC
What is negative selection in the thymus?
T cells that recognise self antigen strongly are eliminated to prevent autoimmunity
Why do T cells need MHC to recognise antigens?
TCRs can only bind to peptides presented on MHC and they cannot see free floating antigens
What determines which T cell subset a naive T cell will become?
Cytokines present during activation
What is the kiss of death in T cell function?
Direct contact between cytotoxic T cell and its target leading to cell lysis
