Why do B cells not undergo positive selection?

Positive selection occurs through antigen-independent signaling involving both the pre-BCR and the BCR. If these receptors do not bind to their ligand, B cells do not receive the proper signals and cease to develop.

What do B cells undergo?

The germinal centre B cells undergo somatic hypermutation and class switch recombination. Plasma cells and memory B cells with a high-affinity for the original antigen stimuli are produced. These cells are long lived and plasma cells may secrete antibody for weeks after the initial infection.

Where do mature naïve B cells go following positive and negative selection?

(a) Naïve B cells Naïve B cells are formed in the bone marrow acquiring B-cell coreceptor (“BCR”) complexes on their surfaces and undergoing processes of positive and negative selection. They then migrate to the spleen and mature to either follicular of marginal-zone naïve B cells.

Why do B cells only undergo negative selection?

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. Signaling for B cell survival and movement through the appropriate stages of gene expression occurs through membrane pre-B receptor and membrane IgM expression.

What is negative selection in immunology?

In immunology Negative selection (immunology), in which B-cells and T-cells that recognize MHC molecules bound to peptides of self-origin, or just MHC molecules with high affinity are deleted from the repertoire of immune cells.

Where do B cells undergo positive selection?

Positive Selection of B Cells Both B and T cells undergo positive and negative selection in the primary lymphoid organs. Positive selection requires signaling through the antigen receptor for the cell to survive. Developing B cells are positively selected when the pre-B receptor binds its ligand.

How do B and T cells differ with respect to antigens that they bind?

T and B cells differ in one fundamental way: whereas T cells bind antigens that have been digested and embedded in MHC molecules by APCs, B cells function as APCs that bind intact antigens that have not been processed.

Where does positive and negative selection of B cells occur?

Developing B cells are positively selected when the pre-B receptor binds its ligand. (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.

Where does positive selection of T cells occur?

In positive selection, T cells in the thymus that bind moderately to MHC complexes receive survival signals (middle).

What is positive selection of T cells?

Positive selection occurs when double positive T cells bind cortical epithelial cells expressing Class I or Class II MHC plus self peptides with a high enough affinity to get the survival signal.