Betz cell

Examples of Betz cell in the following topics:

• Sensory and Motor Tracts

  • In both pathways, primary sensory neuron cell bodies are found in the dorsal root ganglia, and their central axons project into the spinal cord.
  • The corticospinal tract also contains the Betz cell (the largest pyramidal cells) that are not found in any other region of the body.

• Organization of Motor Neuron Pathways

  • The motor impulses originate in the giant pyramidal cells (Betz cells) of the motor area, i.e., the precentral gyrus of the cerebral cortex.
  • The axons of these cells pass from the cerebral cortex to the midbrain and the medulla oblongata.

• Specific T-Cell Roles

  • T helper cells assist the maturation of B cells and memory B cells while activating 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 virus-infected cells and tumor cells, and 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.
  • Regulatory T cells (Treg cells), also known as suppressor T cells, are crucial for the maintenance of immunological tolerance.

• Natural Killer Cells

  • The role of NK cells is similar to that of cytotoxic T cells in the adaptive immune response.
  • NK cells provide rapid responses to virus-infected cells and respond to tumor formation by destroying abnormal and infected cells.
  • NK cells use wo cytolytic granule-mediated apoptosis to destroy abnormal and infected cells.
  • Virus-infected cells destroyed by cell lysis release their replicated virus particles into the body, which infects other cells.
  • Cells that are osponized with antibodies are easier for NK cells to detect and destroy.

• Lymphoid Cells

  • The three major types of lymphocyte are T cells, B cells, and natural killer cells.
  • If cancer cells evade NK cell detection for long enough, however, they can grow into tumors that are more resistant to NK cell activity.
  • T cells are involved in cell-mediated immunity whereas B cells are primarily responsible for humoral immunity.
  • There are two types of T cells involved in adaptive, cell-mediated immunity.
  • Following activation, B cells and T cells leave a lasting legacy of the antigens they have encountered in the form of memory cells.

• Maturation of T Cells

  • T cells belong to a group of white blood cells known as lymphocytes and play a central role in the cell-mediated branch of the adaptive immune system.
  • They are distinguished from other lymphocytes, such as B cells and natural killer cells (NK cells), by the presence of a T cell receptor (TCR) on the cell surface.
  • T cells can be either helper T cells or cytoxic T cells based on whether they express CD4 (helper) or CD8 (cytotoxic) glycoprotein.
  • A T cell is then signaled by the thymus to become a CD4+ cell by reducing expression of its CD8 cell surface receptors.
  • The remaining cells exit the thymus as mature naive T cells.

• Maturation of B Cells

  • B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by T 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.

• Lymphocytes

  • Subtype 2 helper T cells present antigens to B cells.
  • Suppressor T cells (T-reg cells) retain some of their ability to bind to self-cells.
  • Then mature helper T cells bind their antigen to naive B cells through BCRs.
  • Plasma cell and long-lived B cells that are the main source of antibodies.
  • Memory B cells are dormant B cells with the same BCR as the B cell from which they differentiated.

• Clonal Selection and B-Cell Differentiation

  • B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by T cells).
  • 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 is activation of B cells by type 2 helper T cells in the lymph nodes.
  • B cell differentiation is 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.

• Types of Adaptive Immunity

  • Cell mediated immunity is controlled by type 1 helper T cells (Th1) and cytotoxic T cells.
  • Helper T cells facilitate the immune response by guiding cytotoxic T cells to pathogens or pathogen-infected cells, which they will then destroy.
  • Then T-cell produced proteases enter the pathogen and induce an apoptosis response within the cell.
  • Helper T cells secrete cytokines  such as interferon-gamma, which can activate cytotoxic T cells and macrophages.
  • This diagram of adaptive immunity indicates the flow from antigen to APC, MHC2, CD4+, T helper cells, B cells, antibodies, macrophages, and killer T cells.