Lecture 11: Differentiation and Functions of CD8+ T cells Flashcards
CD4 is on what percentage of T cells
66%
CD8 is on what percentage of T cells
33%
T cells make up ___ % of all the lymphocytes in the blood. While B cells comprise the remaining ___% of blood lymphocytes
- T cells: 70%
- B cells: 30%
CD4 cells are what MHC class restricted
Class-II
CD8 cells are what MHC-class restricted
Class-I MHC restricted
Rearrangement of genes of the T cell occurs where in the body
the thymus (this generates a receptor for Ag)
Functional polarization means that the T cell takes on a particular set of tasks that promote the
adaptive immune response. These are often called effector or regulatory functions, depending on their nature
Naive CD8+ cells recognize Ags (signal 1) and proliferate and differentiate in to effector CTLs upon ______ costimulaiton (signal 2)
CD28-CD80
activated CTLs contain numerous granules called lysosomes that contain _____ and _____ used by the cells to kill other cells
perforin and granzymes
Activated CTLs secrete mostly what cytokine
- Mostly IFN-gamma (which potently activate macrophages)
similar to activation of Th1 cells, the molecular events in CTL differentiation involve transcription factor
T-bet
T-bet regulates transcription of genes encoding for ____, ___, and ____ in CD8 cells
- Perforin
- Granzymes
- IFN-gamma
- What is cross presentation
- Dendritic cells canpresent class II MHC-associated peptides generated in the vesicles to CD4+ helper T cells, which are often required to induce full responses of CD8+ cells
- involves the fusion of phagosomes containing the ingested antigens with the ER. Ingested proteins are then translocated from the ER to the cytosol by poorly defined pathways that are likey involved in presentation of proteins degraded in the ER
The full activation of naive CD8+ T cells and their differentiation into functional CTLs and memory cells may require the participation of ______
- CD4+ helper cells
- provide second signal for CD8+ T cells
- secrete cytokines that stimulate differentiation of CD8+ cells
- express CD40L which may bind to CD40 on atigen-loaded dednritic cells. This interaction activates the APCs ot make them more efficient at stimulating the differentiation of CD8+ T cells, in part by inducing the expression of costimulators. This process has been termed licensing of APCs
- There is evidence that CD4+ helper cells are more important for the generation fo CD8+ memory T cells than the differentiation of naive CD8+ T cells into effector CTLs
- provide second signal for CD8+ T cells
Mechanism of APC licensing
- Licensing of the APC occurs when the CD4+ T cell recognizes Ag presented by an MHC class II APC and delivers activating signals through CD80/CD86 and CD40
- CD40-CD40L interaction upregulates expression of CD80/CD86 on professional APCs which makes them more efficient at stimulating the differentiation of CD8+ T cells
- (does not require CD4+ and CD8+ T cells to be in contact with APC at the same time)
CD4+ helper T cells are required for CD8+ T cell responses when ______ innate immune reactions are evoked by
- Relatively weak innate immune responses
- latent viral infections, organ transplants, and tumors
CD4+ helper t cells provide signal ___ in form of cytokines which enhance activation of CTLs
3