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:

  • Maturation of B Cells

    • Immature B cells are produced in the bone marrow and migrate to secondary lymphoid tissues where some develop into mature B cells.
    • Once a B cell encounters its cognate antigen and receives an additional signal from a T helper cell, it can further differentiate into either plasma B cells or memory B cells.
    • B cells exist as clones.
    • A single B cell or a clone of cells with shared specificity, upon encountering its specific antigen, divides to produce many B cells.
    • B cells that encounter antigen for the first time are known as naive B cells.
  • Clonal Selection and B-Cell Differentiation

    • However, B cell recognition of antigens is not the only element necessary for B cell activation.
    • B cells that have not been exposed to antigen, also known as naïve B cells, can be activated in a T cell-dependent or -independent manner.
    • T Cell Dependent Activation- activation of B cells by type 2 helper T cells in the lymph nodes.
    • B Cell differentiation refers to the process by which B cells change into different types, such as plasma cells and plasma blasts.
    • T cell-dependent B cell activation, showing a TH2-cell (left), B cell (right), and several interaction molecules
  • Lymphocytes

    • Subtype 2 helper T cells present antigens to B cells.
    • Then mature helper T cells bind their antigen to naive B cells through their BCR.
    • Plasma Cell- long-lived B cells that are the main source of antibodies.
    • Regulatory B Cell (Breg cell)- immunosuppresive B cells that secrete anti-inflammatory cytokines (such as IL-10) to inhibit autoimmune lymphocytes.
    • Memory B Cells- dormant B cells that have the same BCR as the cell the B cell they differentiated from, and are specific to the antigen presented to that BCR.
  • 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
  • Making Memory B Cells

    • Memory B cells are a B cell sub-type that are formed following primary infection.
    • Memory B cells are a B cell sub-type that are formed following a primary infection .
    • Most of them differentiate into the plasma cells, also called effector B cells (which produce the antibodies) and clear away with the resolution of infection.
    • To understand the events taking place, it is important to appreciate that the antibody molecules present on a clone (a group of genetically identical cells) of B cells have a unique paratope (the sequence of amino acids that binds to the epitope on an antigen).
    • B lymphocytes are the cells of the immune system that make antibodies to invading pathogens like viruses.
  • Cell-Mediated Autoimmune Reactions

    • A normal immune response is assumed to involve B and T cell responses to the same antigen, where B cells recognize conformations on the surface of a molecule for B cells, and T cells recognize pre-processed peptide fragments of proteins for T cells.
    • Roosnek and Lanzavecchia showed that B cells recognizing IgGFc could get help from any T cell that responds to an antigen co-endocytosed with IgG by the B cell as part of an immune complex.
    • Together with the concept of T cell-B cell discordance, this idea forms the basis of the hypothesis of self-perpetuating autoreactive B cells.
    • Autoreactive B cells in spontaneous autoimmunity are seen as surviving because of subversion both of the T cell help pathway and of the feedback signal through the B cell receptor.
    • In this process T-cells are stimulated to grow and can signal B-cells to produce antibodies.
  • Tests That Differentiate Between T Cells and B cells

    • Methods used to differentiate T cells and B cells include staining cell surface receptors and functional assays like the T lymphocyte cytotoxicity assay.
    • B-cells are also white blood cells and are a vital part of the humoral immunity branch of the adaptive immune system.
    • T-lymphocytes can be distinguished from other lymphocytes like B cells and natural killer cells (NK cells) by the presence of a T cell receptor (TCR) on the cell surface.
    • Alternatively, B-cells can be distinguished from other lymphocytes like T cells and natural killer cells (NK cells) by the presence of a protein on the B-cell's outer surface called a B-cell receptor (BCR).
    • The expression of different markers allows the separation/differentiation of T and B cells.
  • 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
  • Lymphoid Cells

    • The three major types of lymphocyte are T cells, B cells, and natural killer cells.
    • T cells are involved in cell-mediated immunity whereas B cells are primarily responsible for humoral immunity.
    • They present antigens to B cells, produce cytokines that guide cytotoxic T cells, and activate macrophages.
    • B cells are part of the humoral component of adaptive immunity.
    • B cells mature into B lymphocytes in the bone marrow, while T cells migrate to and mature in thymus.
  • Specific T-Cell Roles

    • T helper cells assist the maturation of B cells and memory B cells while activating cytotoxic T cells and macrophages.
    • Their primary functions include antigen presentation and activation of B cells, and activation of cytotoxic T cells and macrophages.
    • Differentiation into helper T cell subtypes occurs during clonal selection following T cell activation of naive T cells.
    • Cytotoxic T cells (TC cells, or CTLs) destroy virally infected cells and tumor cells, and are also cause much of the damage in in transplant rejection and autoimmune diseases.
    • Memory T cells comprise two subtypes: central memory T cells (TCM cells) and effector memory T cells (TEM cells), which have different properties and release different cytokines.
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