germinal centers

(noun)

Places within secondary lymph nodes to which B cells migrate to proliferate and differentiate based on an antigen response.

Related Terms

Examples of germinal centers in the following topics:

  • Making Memory B Cells

    • All these events occur in the highly "eventful" germinal centers of lymphoid follicles, within the lymph nodes.

  • Tonsils

    • Captured antigens are presented to B and T cells within the tonsil, then the B cells migrate to germinal centers within the tonsil as an adaptive immune response is initiated.

  • 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.

  • Lymph Transport

    • When a lymphocyte is presented with an antigen (such as by an activated helper T cell), B cells become activated and migrate to the germinal centers of the node, where they proliferate and differentiate to be specific to that antigen.
    • Four pairs of lymph trunks are distributed laterally around the center of the body, along with an unpaired intestinal trunk.

  • Clonal Selection and B-Cell Differentiation

    • After activation, the B cell will then undergo differentiation and clonal expansion, which usually involves migrating to germinal centers should the activation take place in a lymph node.

  • Subtropical Deserts and Chaparral

    • Subtropical deserts, which exist between 15° and 30° north and south latitude, are centered on the Tropics of Cancer and Capricorn.
    • The chaparral vegetation is dominated by shrubs and is adapted to periodic fires, with some plants producing seeds that only germinate after a hot fire .
    • Some plants produce seeds that only germinate after a hot fire.

  • Basidiomycota: The Club Fungi

    • The haploid nuclei migrate into basidiospores, which germinate and generate monokaryotic hyphae.
    • As it grows, the mycelium depletes the soil of nitrogen, causing the mycelia to grow away from the center, leading to the "fairy ring" of fruiting bodies where there is adequate soil nitrogen.

  • Anthrax

    • The endospores germinate at the site of entry into the tissues and then spread via the circulation to the lymphatics, where the bacteria multiply.
    • It first appears as a boil-like lesion then eventually forms a painless ulcer with a black center.

  • Development of the Seed

    • This tissue becomes the food the young plant will consume until the roots have developed after germination.
    • Upon germination, enzymes are secreted by the aleurone, a single layer of cells just inside the seed coat that surrounds the endosperm and embryo.
    • Upon germination in dicot seeds, the epicotyl is shaped like a hook with the plumule pointing downwards; this plumule hook persists as long as germination proceeds in the dark.
    • As the seed germinates, the primary root emerges, protected by the root-tip covering: the coleorhiza.
    • Upon a return to optimal conditions, seed germination takes place.

  • Fruit and Seed Dispersal

    • Seeds contained within fruits need to be dispersed far from the mother plant so that they may find favorable and less-competitive conditions in which to germinate and grow.
    • Coconuts are well known for their ability to float on water to reach land where they can germinate.
    • Some animals, such as squirrels, bury seed-containing fruits for later use; if the squirrel does not find its stash of fruit, and if conditions are favorable, the seeds germinate.
    • Dormant seeds can wait months, years, or even decades for the proper conditions for germination and propagation of the species.