B cell

(noun)

a lymphocyte, developed in the bursa of birds and the bone marrow of other animals, that produces antibodies and is responsible for the immune system

Related Terms

  • T cell
  • epitope
  • immunoglobulin
  • antigen

Examples of B cell in the following topics:

  • Antigen-presenting Cells: B and T cells

    • Whether an immature lymphocyte becomes a B cell or T cell depends on where in the body it matures.
    • Upon antigen binding to a B cell receptor, a signal is sent into the B cell to turn on an immune response.
    • Unlike B cells, T cells do not directly recognize antigens.
    • B cell receptors are embedded in the membranes of B cells and bind a variety of antigens through their variable regions, or antibodies.
    • Explain the role played by B and T cells in the adaptive immune system
  • Humoral Immune Response

    • B cells are the major cell type involved in the humoral immune response.
    • Each B cell initially produced has only one kind of antibody (antigen receptor), which makes every B cell unique.
    • When this process is complete, the B cell is sensitized.
    • These daughter cells become either plasma cells or memory B cells.
    • The memory B cells remain inactive at this point.
  • Immunological Memory

    • As B cells and T cells mature into effector cells, a subset of the naïve populations differentiates into B and T memory cells with the same antigen specificities .
    • After initially binding an antigen to the B cell receptor (BCR), a B cell internalizes the antigen and presents it on MHC II.
    • A helper T cell recognizes the MHC II–antigen complex and activates the B cell.
    • As a result, memory B cells and plasma cells are made.
    • Describe the role of memory B and T cells in immulogical memory
  • Regulating Immune Tolerance

    • Immune tolerance of self and harmless antigens occurs by deleting B and T cells that recognize those antigens, often near mucosal surfaces.
    • APCs of the mucosal immune system are primarily dendritic cells, with B cells and macrophages playing minor roles.
    • Antigen-presenting cells, T cells, and B cells aggregate within the Peyer's patch, forming organized lymphoid follicles.
    • There, some T cells and B cells are activated.
    • Other antigen-loaded dendritic cells migrate through the lymphatic system where they activate B cells, T cells, and plasma cells in the lymph nodes.
  • Cell-Mediated Immunity

    • Just as the humoral immune response has B cells which mediate its response, the cellular immune response has T cells, which recognize infected cells and destroy them before the pathogen inside can replicate and spread to infect other cells.
    • Unlike B cells, T lymphocytes (T cells) are unable to recognize pathogens without assistance.
    • Once activated, the TC creates a large clone of cells with one specific set of cell-surface receptors, similar to the proliferation of activated B cells.
    • As with B cells, the clone includes active TC cells and inactive memory TC cells.
    • B plasma cells and TC cells are collectively called effector cells because they are involved in "effecting" (bringing about) the immune response of killing pathogens and infected host cells.
  • White Blood Cells

    • The second main group is the agranulocytes, which lack granules in their cytoplasm, and include the monocytes and lymphocytes ( b).
    • They include B cells, T cells, and natural killer cells.
    • B cells destroy bacteria and inactivate their toxins; they also produce antibodies.
    • (b) Agranulocytes include lymphocytes and monocytes.
    • Lymphocytes, including B and T cells, are responsible for adaptive immune response.
  • Cytotoxic T Lymphocytes and Mucosal Surfaces

    • B cell maturation occurs in the bone marrow, whereas progenitor cells migrate from the bone marrow and develop and mature into naïve T cells in the organ called the thymus.
    • On maturation, T and B lymphocytes circulate to various destinations.
    • Lymph nodes scattered throughout the body house large populations of T and B cells, dendritic cells, and macrophages .
    • The spleen houses B and T cells, macrophages, dendritic cells, and NK cells .
    • The liquid passes through (b) lymph nodes that filter the lymph that enters the node through afferent vessels, leaving through efferent vessels.
  • Cells as the Basic Unit of Life

    • A cell is the smallest unit of a living thing.
    • A living thing, whether made of one cell (like bacteria) or many cells (like a human), is called an organism.
    • For example, both animal and plant cells are classified as eukaryotic cells, whereas bacterial cells are classified as prokaryotic.
    • Bone cells help to support and protect the body.
    • (a) Nasal sinus cells (viewed with a light microscope), (b) onion cells (viewed with a light microscope), and (c) Vibrio tasmaniensis bacterial cells (seen through a scanning electron microscope) are from very different organisms, yet all share certain characteristics of basic cell structure.
  • The Role of the Cell Cycle

    • Single-celled organisms use cell division as their method of reproduction.
    • While there are a few cells in the body that do not undergo cell division, most somatic cells divide regularly.
    • A somatic cell is a general term for a body cell: all human cells, except for the cells that produce eggs and sperm (which are referred to as germ cells), are somatic cells.
    • The cell cycle is an ordered series of events involving cell growth and cell division that produces two new daughter cells.
    • After four rounds of cell division, (b) there are 16 cells, as seen in this SEM image.
  • Gene Expression in Stem Cells

    • In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues.
    • Stem cells can now be artificially grown and differentiated into specialized cell types with characteristics consistent with muscle or nerve cells through cell culture.
    • In one, the daughter cells are initially equivalent but a difference is induced by signaling between the cells, from surrounding cells, or from the precursor cell.
    • Stem cells are indicated by (A), progenitor cells by (B), and differentiated cells by (C).
    • Pluripotent, embryonic stem cells originate as inner cell mass (ICM) cells within a blastocyst.
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