Immunology 4 - Initiation of Acquired Immune Responses Flashcards
What is the only type of antigen T cells can recognise?
Peptide antigens
What is a T cell antigen receptor?
A membrane bound protein heterodimer (formed by two different proteins)
What present peptide antigens to T cells?
MHC molecules
Do B cells require MHC molecules in order to ‘see’ an antigen?
No
What does MHC stand for?
Major Histocompatibility Complex
What are the features of class 1 MHC molecules?
Expressed on all nucleated cells
Present peptide antigens to CD8+T cells
What are CD8+T cells?
Cells that express a CD8 protein
What are the features of class 2 MHC molecules?
Expressed only on professional antigen presenting cells (APCs) such as dendritic cells, macrophages and B cells
Present peptide antigen to CD4+T cells
What is the main function of dendritic cells?
To process and present antigens on their cell surface to T cells
Where are dendritic cells present in large numbers?
Tissues that are in contact with the external environment like the skin
Are dendritic cells phagocytic?
Yes
What is the effect of pro-inflammatory TNFalpha on dendritic cells?
Stimulates them to mature and increase expression of co-stimulatory molecules
What do dendritic cells do after phagocytosing pathogenic antigens?
Break these proteins down into short peptides Then load them onto class 1 and 2 MHC molecules which are transported to the cell surface
What signal do T cells require to be activated?
Co-stimulatory molecules expressed by dendritic cells
Why do T cells require a second signal to be activated?
To ensure they only activate in event of infection
What are naive T cells called?
CD4+T cells
What are proliferating T cells known as?
Th0 cells
What types of helper T cells can T cells differentiate into?
Th1
Th2
Tfh
Regulatory T cells
What does Tfh stand for?
Folicular helper T cells
What is a naive T cell?
One that has never encountered a pathogen
What growth factor do antigen activated CD+4 T cells start to secrete and what do they express?
Interleukin 2 (IL-2) Interleukin 2 receptor
What do Th0 cells induce?
Proliferation of CD4+ and CD8+ cells
Where do Th1 cells move to from the lymph nodes?
Infected tissues
What is the function of Th1 cells?
Secrete pro-inflammatory cytokines to enhance macrophages
Where do Tfh cells move to?
B cell zone
What is the function of Tfh cells?
Stimulate B cells to clonal proliferate and differentiate into long-lived plasma cells and long-lived memory cells
What do antigen-activated CD8+ cells differentiate into?
Cytotoxic T cells/lymphocytes (CTLs)
Where do CTLs migrate to?
Site of infection
What is the function of CTLs?
To kill virally infected host cells
How do CTLs kill virally infected host cells?
Inducing apoptosis
