clonal selection

(noun)

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.

Related Terms

Examples of clonal selection in the following topics:

  • 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.
    • The preservation of useful specificities is called positive selection.
    • 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 of Antibody-Producing Cells

    • The clonal selection hypothesis is a widely accepted model for the immune system's response to infection.
    • The clonal selection hypothesis has become a widely accepted model for how the immune system responds to infection and how certain types of B and T lymphocytes are selected for destruction of specific antigens invading the body .
    • Talmage, worked on this model and was the first to name it "clonal selection theory. " Burnet explained immunological memory as the cloning of two types of lymphocyte.
    • 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.
    • Describe the clonal selection hypothesis in regards to the production of B cells

  • 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.

  • The Heat-Shock Response

    • This is an example of small heat shock proteins produced by Pseudomonas aeruginosa Clonal Variants Isolated from Diverse Niches.

  • Generation Time

    • It emphasizes clonality, asexual binary division, the short development time relative to replication itself, the seemingly low death rate, the need to move from a dormant state to a reproductive state or to condition the media, and finally, the tendency of lab adapted strains to exhaust their nutrients.

  • Selective and Differential Media

    • Selective media are used for the growth of only selected microorganisms.
    • Selective growth media for eukaryotic cells commonly contain neomycin to select cells that have been successfully transfected with a plasmid carrying the neomycin resistance gene as a marker.
    • Some examples of selective media include:
    • Mannitol salt agar (MSA) which is selective for Gram-positive bacteria and differential for mannitol.
    • Xylose lysine desoxyscholate (XLD), which is selective for Gram-negative bacteria buffered charcoal yeast extract agar, which is selective for certain gram-negative bacteria, especially Legionella pneumophila.

  • Metagenomics

    • While traditional microbiology and microbial genome sequencing and genomics rely upon cultivated clonal cultures, early environmental gene sequencing cloned specific genes (often the 16S rRNA gene) to produce a profile of diversity in a natural sample.

  • Antibiotics and Selective Toxicity

    • Antibiotics are able to selectively target specific types of bacteria without harming the infected host.
    • He then proposed the idea that it might be possible to create chemicals that would act as a selective drug that would bind to and kill bacteria without harming the human host.
    • The remainder must be tested for their selective toxicities and therapeutic activities, and the best candidates can be examined and possibly modified.
    • In antibacterial production, microorganisms must be isolated, cultured, and tested for growth inhibition of target organisms and for their selective toxicity.

  • Selection

    • A selectable marker is usually a gene that confers resistance to an antibiotic that would otherwise kill the cells.
    • Scientists who do experimental genetics employ artificial selection experiments that permit the survival of organisms with user-defined phenotypes.
    • Artificial selection is widely used in the field of microbial genetics, especially molecular cloning.
    • Experimental scientists deal with this issue through a step of artificial genetic selection , in which cells that have not taken up DNA are selectively killed, and only those cells that can actively replicate DNA containing the selectable marker gene encoded by the vector are able to survive.
    • When bacterial cells are used as host organisms, the selectable marker is usually a gene that confers resistance to an antibiotic that would otherwise kill the cells, typically ampicillin.

  • Biological Control of Microbes

    • A number of factors affect selection of the best agent for any given situation - Antimicrobial agents must be selected with specific organisms and environmental conditions in mind.
    • Additional variables to consider in the selection of an antimicrobial agent include pH, solubility, toxicity, organic material present, and cost.
    • Once an agent has been selected, it is important to evaluate it's effectiveness.