clonal deletion

(noun)

A process by which B cells and T cells are deactivated after they have expressed receptors for self-antigens and before they develop into fully immunocompetent lymphocytes.

Examples of clonal deletion in the following topics:

  • Clonal Selection and B-Cell Differentiation

    • B cells undergo clonal selection and develop similarly to T cells with some notable differences.
    • When the B cell fails in any step of the maturation process, it will die by apoptosis, here called clonal deletion.
    • If these B cells have high affinity for binding to self-antigens, they will die by clonal deletion or another pathway such as anergy.
    • Clonal expansion is the process by which daughter cells arise from a parent cell.
    • During B cell clonal expansion, many copies of that B cell are produced that share affinity with and specificity of the same antigen.

  • Maturation of B Cells

    • When the B cell fails in any step of the maturation process, it will die by a mechanism called apoptosis, or specifically, clonal deletion.
    • Such clonality has important consequences because immunogenic memory relies on it.

  • Lymphocytes

    • Instead of apoptosis, though, defective B cells are killed through other mechanisms such as clonal deletion.

  • Clonal Selection and T-Cell Differentiation

    • Clonal selection is an theory that attempts to explain why lymphocytes are able to respond to so many different types of antigens.
    • Clonal selection assumes that lymphocytes are selected during antigen presentation because they already have receptors for that antigen.
    • This mass production is termed "clonal expansion," in which daughter cells proliferate into several generations of clones of the original parent cells.
    • Clonal selection may also be used during negative selection during T cell maturation.
    • Clonal selection is thought to cause mutations of antigen-binding affinity in memory cells during clonal expansion so that memory cells have greatly increased antigen-binding affinity than the effector cells during the first response.

  • Lymphoid Tissue

    • During antigen presentation, such as from the dendritic cells, lymphocytes migrate to germinal centers of the secondary lymphoid tissues, where they undergo clonal expansion and affinity maturation.

  • Cystic Fibrosis

    • The ΔF508 human genome mutation is characterized by the deletion of three base pairs in the CFTR nucleotide sequence, causing the loss of the amino acid phenylalanine located at position 508 .
    • The ΔF508 human genome mutation is characterized by the deletion of three base pairs in the CFTR nucleotide sequence, causing the loss of the amino acid phenylalanine located at position 508.

  • Aging and the Immune System

    • the accumulation and the clonal expansion of memory and effector T-cells

  • Maturation of T Cells

    • As its functional mass shrinks by about 3% a year throughout middle age, there is a corresponding fall in the thymic production of naive T cells, leaving clonal expansion of immature T cells to play a greater role in protecting older subjects.

  • Specific T-Cell Roles

    • Differentiation into helper T cell subtypes occurs during clonal selection following T cell activation of naive T cells.

  • Immunological Memory

    • Memory cells derive from their parent B and T cells, and undergo clonal selection following infection, which increases antigen-binding affinity.