cell

Examples of cell in the following topics:

• Cellular Differentiation

  • Three basic categories of cells make up the mammalian body: germ cells, somatic cells, and stem cells.
  • Pluripotent stem cells undergo further specialization into multipotent progenitor cells that then give rise to functional cells.
  • Hematopoietic stem cells (adult stem cells) from the bone marrow that give rise to red blood cells, white blood cells, and platelets
  • Mesenchymal stem cells (adult stem cells) from the bone marrow that give rise to stromal cells, fat cells, and types of bone cells;
  • Epithelial stem cells (progenitor cells) that give rise to the various types of skin cells

• 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.

• Dendritic Cells

  • Dendritic cells are immune cells that function to process antigens and present them to T cells.
  • Immature dendritic cells (e.g.
  • Mature dendritic cells reside in the T cell zones of the lymph nodes, and in this location they display antigens to T cells.
  • Dendritic cells are constantly in communication with other cells in the body.
  • This communication can take the form of direct cell-to-cell contact based on the interaction of cell-surface proteins.

• Cell Theory

  • Cell theory states: living things are composed of one or more cells; the cell is the basic unit of life; cells arise from existing cells.
  • The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells.
  • "All cells only arise from pre-existing cells.
  • Cells carry genetic material passed to daughter cells during cellular division
  • The cell is the basic unit of life and the study of the cell led to the development of the cell theory.

• 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 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.
  • Regulatory T cells (Treg cells), also known as suppressor T cells, are crucial for the maintenance of immunological tolerance.

• The Role of the Cell Cycle

  • In other words, that original single cell is the ancestor of every other cell in the body.
  • 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.

• Classes of T Cells

  • T cells play a central role in cell-mediated immune response through the use of the surface T cell receptor to recognize peptide antigens.
  • T cells do not produce antibody molecules.
  • Effector cells include helper T cells, and cytolytic or cytotoxic T cells.
  • Another class of T cells called regulatory T cells function to inhibit immune response and resolve inflammation.
  • T cells promote the killing of cells that have ingested microorganisms and present foreign antigens on their surface.

• Natural Killer Cells

  • Natural killer cells (NK cells) are cytotoxic lymphocyte critical to the innate immune system.
  • The role of NK cells is similar to that of cytotoxic T cells in the adaptive immune response.
  • NK cells provide rapid responses to virally infected cells and respond to tumor formation by destroying abnormal and infected cells.
  • NK cells use two cytolytic granule mediated apoptosis to destroy abnormal and infected cells.
  • Typically, immune cells detect major histocompatibility complex (MHC) presented on cell surfaces, triggering cytokine release and lysis or apoptosis in cells that do not express MHC I, or express much less of it than normal cells.

• Natural Killer Cells

  • After a pathogen enters the body, infected cells are identified and destroyed by natural killer (NK) cells, which are a type of lymphocyte that can kill cells infected with viruses or tumor cells (abnormal cells that uncontrollably divide and invade other tissue).
  • As such, NK cells offer a complementary check for unhealthy cells, relative to T cells.
  • NK cells are always active; an interaction with normal, intact MHC I molecules on a healthy cell disables the killing sequence, causing the NK cell to move on.
  • After the NK cell detects an infected or tumor cell, its cytoplasm secretes granules comprised of perforin: a destructive protein that creates a pore in the target cell.
  • Phagocytic cells then digest the cell debris left behind.

• Regulation of the Cell Cycle by External Events

  • External factors can influence the cell cycle by inhibiting or initiating cell division.
  • Each cell is produced as part of its parent cell.
  • Some cells do live longer than others, but eventually all cells die when their vital functions cease.
  • Crowding of cells can also inhibit cell division.
  • Another factor that can initiate cell division is the size of the cell; as a cell grows, it becomes inefficient due to its decreasing surface-to-volume ratio.