clonal deletion

Examples of clonal deletion in the following topics:

• Clonal Selection and B-Cell Differentiation

  • B Cells develop in way that is similar but different to T cells, and undergo clonal selection
  • 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 through 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 the affinity 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, defective B cells are killed through various mechanisms, such as clonal deletion.

• Clonal Selection of Antibody-Producing Cells

  • The clonal selection hypothesis is a widely accepted model for the immune system's response to infection.
  • Those lymphocytes bearing receptors for self molecules will be deleted at an early stage.
  • In 1958, Sir Gustav Nossal and Joshua Lederberg showed that one B cell always produces only one antibody, which was the first evidence for clonal selection theory.
  • Such clonality has important consequences, as immunogenic memory relies on it .
  • Describe the clonal selection hypothesis in regards to the production of B cells

• Clonal Selection and Tolerance

  • Clonal selection and tolerance select for survival of lymphocytes that will protect the host from foreign antigens.
  • Clonal selection occurs after immature lymphocytes express antigen receptors.
  • clonal selection of the B and T lymphocytes:1.
  • Describe the importance of central and peripheral tolerance and distinguish between positive and negative clonal selection

• 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 already have receptors for that antigen, and are selected during antigen presentation because they already have that unique antigen receptor.
  • This mass production of daughter cells 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.

• Deletion

  • Product deletion, either through product replacement or product elimination, results when products fail to meet company expectations.
  • As a result, companies are under pressure to evaluate their existing product line and to make continuous decisions about adding new products or deleting existing ones.
  • Deletion is the process of removing products that perform below market expectations or fail to meet company objectives.
  • Deletion results in either product replacement or product elimination.
  • In addition to weak sales and profit, brands delete products that fail to align with marketing strategies, or that demonstrate an unfavorable market outlook.

• Introduction

  • understand the strategic importance of adding and deleting products. understand some methods which can be applied to assist in this decision-making process
  • be able to discuss the related topics of failed innovation and product deletion
  • As a result, organizations are under pressure to evaluate their existing product line and to make continuous decisions about adding new products or deleting existing products.
  • In the past, four of these products have been deleted (the products labeled as A, B, C, and F).
  • (b) product categories; (c) Innovation through business models; (d) Evaluating innovations; (e) When innovation fails: deleting products; and (f) chapter summary.

• Antimicrobial Peptides

  • In contrast to the clonal, acquired adaptive immunity, endogenous peptide antibiotics or antimicrobial peptides provide a fast and energy-effective mechanism as front-line defense.

• Bacterial Genomes

  • Compelling evidence indicates that the apparent degradation of bacterial genomes is owed to a deletional bias.
  • Deletional bias selection is but one process involved in evolution.
  • Evidence of a deletional bias is present in the respective genome sizes of free-living bacteria, facultative and recently derived parasites and obligate parasites and symbionts.
  • As such, in recently formed and facultative parasites, there is an accumulation of pseudogenes and transposable elements due to a lack of selective pressure against deletions.
  • The population bottlenecks reduce gene transfer and as such, deletional bias ensures the reduction of genome size in parasitic bacteria.