Clonal deletion is the removal through apoptosis of B cells and T cells that have expressed receptors for self before developing into fully immunocompetent lymphocytes. Central tolerance prevents B and T lymphocytes from reacting to self. Thus, clonal deletion can help protect individuals against autoimmunity.
What is clonal expansion quizlet?
Clonal expansion is the: production of daughter cells all arising originally from a single cell. In a clonal expansion of lymphocytes, all progeny share the same antigen specificity.
Where does clonal deletion take place?
Clonal deletion can occur centrally during the initial differentiation of antigen-specific T cells or B cells or even later in peripheral sites. In the case of T cells, the site of T cell differentiation is the thymus (Sprent and Webb, 1995).
What is meant by the clonal selection hypothesis?
Key Terms. clonal selection: An hypothesis which states that an individual lymphocyte (specifically, a B cell) expresses receptors specific to the distinct antigen, determined before the antibody ever encounters the antigen. Binding of Ag to a cell activates the cell, causing a proliferation of clone daughter cells.
How is clonal deletion related to autoimmune disease?
Clonal deletion reliably removes all T cells that can mount aggressive responses against self MHC molecules; the organ-specific autoimmune diseases, which involve rare T-cell responses to a particular self peptide bound to a self MHC molecule, are therefore unlikely to reflect a general failure in clonal deletion; nor …
Which of the following is produced by cytotoxic T cell?
Cytokine Secretion Cytotoxic T cells release two cytokines in particular, TNF-alpha and IFN-gamma, which facilitate the activation of macrophages. The macrophages attack and clean up infected cells and prevent unregulated cell growth such as that of a tumor.
What occurs during clonal selection?
During clonal selection, random mutations during clonal expansion cause the production of B cells with increased antibody-binding affinity for their antigens. The clonal selection hypothesis may explain why secondary immune responses are so effective at preventing reinfection by the same pathogen.
What is an example of clonal selection?
Clonal selection theory of lymphocytes: 1) A hematopoietic stem cell undergoes differentiation and genetic rearrangement to produce 2) immature lymphocytes with many different antigen receptors. Those that bind to 3) antigens from the body’s own tissues are destroyed, while the rest mature into 4) inactive lymphocytes.
What happens during clonal selection?
