positive and negative selection of t cells ppt

1. What is positive and negative selection of T cells?
2. Where does positive and negative selection of T cells occur?
3. What is the purpose of positive selection during T cell development?
4. Why is negative selection important in both T cell and B cell development?
5. What are the 4 types of T cells?
6. What is positive selection pressure?
7. What are the two major goals of T cell development?
8. Where do T cells undergo positive selection?
9. Why is positive selection important?

What is positive and negative selection of T cells?

In positive selection, T cells in the thymus that bind moderately to MHC complexes receive survival signals (middle). However, T cells whose TCRs bind too strongly to MHC complexes, and will likely be self-reactive, are killed in the process of negative selection (bottom).

Where does positive and negative selection of T cells occur?

T cell development occurs in the thymus; the thymic microenvironment directs differentiation as well as positive and negative selection.

What is the purpose of positive selection during T cell development?

Differentiation of αβ T cell receptor (TCR)-expressing T cells involves an obligatory interaction with self-major histocompatibility complex (MHC) molecules in the thymus. This process, called positive selection, both rescues thymocytes from programmed cell death and induces their differentiation into mature T cells.

Why is negative selection important in both T cell and B cell development?

(Developing T cells are positively selected for their ability to bind MHC as well as peptide.) Negative selection means that binding to the receptor results in cell death. Both immature B and T cells are negatively selected if they bind self antigen.

What are the 4 types of T cells?

There are 3 main types of T cells: cytotoxic, helper, and regulatory. Each of them has a different role in the immune response. Cytotoxic T cells (Tc cells) have a co-receptor called CD8 on their cell surface.

What is positive selection pressure?

Positive selection: also called (Darwinian selection) variants that increase in frequency until they fix in the relevant population. The selective pressure that leads to this fixation is termed positive selection. ... Variation and selection depend from the non-spontaneous and spontaneous processes.

What are the two major goals of T cell development?

Answer: The two goals are (1) to ensure that all T cells have functional TCR and that (2) autoreactive cells are deleted (self-tolerance in ensured).

Where do T cells undergo positive selection?

T cells undergo positive and negative selection in the thymic cortex and medulla, respectively. A promiscuous expression of a wide array of self-anti- gens in the thymus is essential for the negative selection of self-reactive T cells and the establishment of central tolerance.

Why is positive selection important?

In this theory T cell receptors diversity is required for cells to sense differently different peptides; positive selection is needed to guarantee maximal lymphocyte's interactivity and to allow negative selection to reduce conjugation lifetimes maximally; costimulation is necessary to signal that an antigen presenting ...