T lymphocytes

(noun)

These cells, also called T cells, belong to a group of white blood cells known as lymphocytes and play a central role in cell-mediated immunity. 

Related Terms

Examples of T lymphocytes in the following topics:

  • Thymus

    • The thymus is a specialized organ that "educates" T cells or T lymphocytes, which are part of the adaptive immune system.
    • It consists of primary lymphoid tissue, which provides a site for the generation and maturation of T lymphocytes, critical cells of the adaptive immune system.
    • Histologically, the thymus contains mature lymphocytes, immature lymphocytes, and stroma, while lobule tissues consist of an inner medulla and an outer cortex.
    • Then the T cells are sorted by the thymus so that only T cells that express T-cell receptors (TcRs) and can bind to foreign MHC molecules will survive.
    • Autoimmune diseases occur when central tolerance is lost, which causes lymphocytes to recognize host molecules as antigens and attack them, even if those tissues otherwise function normally.

  • Lymph Nodes

    • Lymph nodes are the primary site for antigen presentation and activation in adaptive immune response in B and T lymphocytes.
    • These lymphocytes are continuously recirculated through the lymph nodes and the bloodstream.
    • There, antigen-presenting cells called dendritic cells present the antigen molecule to naive B and T lymphocytes.
    • These undergo cell cycle proliferation into lymphocytes that are able to specifically detect and eliminate pathogens associated with that antigen, through various methods such as cytotoxic action (T cells) and antibody production (B cells).
    • The lymph node is also arranged in such a way that the chance of B and T lymphocytes encountering dendritic cells is quite high, to facilitate antigen presentation.

  • Lymphoid Tissue

    • Specialized lymphoid tissue supports proliferation and differentiation of lymphocytes.
    • The thymus gland and bone marrow contain primary lymphoid tissue where B and T cells are generated.
    • T cells mature in the thymus, while B cells mature in the bone marrow.
    • T cells born in bone marrow travel to the thymus gland to mature.
    • In addition to supporting B and T lymphocyte activation, other secondary lymphoid organs perform other unique functions, such as the spleen's ability to filter blood and the tonsil's ability to capture antigens in the upper respiratory tract.

  • Types of WBCs

    • Lymphocytes, which come in three types.
    • B-lymphocytes produce antibodies in the humoral immune response.
    • T-lymphocytes participate in the cell-mediated immune response.
    • B and T lymphocytes contain MHC antigen receptors and their activity is antigen-specific.
    • They phagocytize pathogens and present antigens to naive lymphocytes.

  • Lymphocytes

    • A lymphocyte is a type of white blood cell in the vertebrate immune system.
    • A lymphocyte is a type of white blood cell in the immune system, including both the B and T cells of the adaptive immune system and natural killer (NK) cells of the innate immune system .
    • While these are the main categories of T lymphocytes, there are other subtypes within these categories as well as additional categories that are not fully understood.
    • Regulatory B cells (B reg cells) are immunosuppresive B cells that secrete anti-inflammatory cytokines (such as IL-10) to inhibit autoimmune lymphocytes.
    • A scanning electron microscope (SEM) image of a single human lymphocyte.

  • Lymphoid Cells

    • The three major types of lymphocyte are T cells, B cells, and natural killer cells.
    • T and B lymphocytes are the main forces of adaptive immunity, which includes cell-mediated and humoral immunity.
    • Sometimes these lymphocytes react to antigens that aren't harmful (allergy) or will attack antigens expressed from the host's own body (autoimmunity).
    • B cells mature into B lymphocytes in the bone marrow, while T cells migrate to and mature in thymus.
    • The lymphocytes involved in adaptive immunity (B and T cells) differentiate further after exposure to an antigen, which occurs in the lymph nodes during antigen presentation from the dendritic cells.

  • Antigen-Presenting Cells

    • Several different types of T cell can be activated by professional APCs, and each type of T cell is specially equipped to deal with different pathogens, whether the pathogen is bacterial, viral or a toxin.
    • MHC Class I molecules present antigen to CD8+ cytotoxic T cells.
    • Cytotoxic T cells (also known as TC, killer T cell, or cytotoxic T-lymphocyte (CTL)) are a population of T cells that are specialized for inducing the death of other cells.
    • CD4+ lymphocytes, or TH, are immune response mediators, and play an important role in establishing and maximizing the capabilities of the adaptive immune response.
    • In the lower pathway; whole foreign proteins are bound by membrane antibodies (5) and presented to B lymphocytes (6), which process (7) and present antigen on MHC II (8) to a previously activated T helper cell (10), spurring the production of antigen-specific antibodies (9).

  • 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.
    • This insures T cell functionality since T cells with non-functional receptors cannot receive antigens and are thus useless to the immune system.
    • Scanning electron micrograph of T lymphocyte (right), a platelet (center), and a red blood cell (left).

  • Natural Killer Cells

    • Natural killer (NK) cells are cytotoxic lymphocytes critical for the innate immune system.
    • Natural killer (NK) cells are cytotoxic lymphocytes 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 are large granular lymphocytes derived from the common lymphoid progenitor cells (lymphoblasts), which also generate B and T lymphocytes.
    • Most of these receptors are also present in certain T cells.

  • Clonal Selection and T-Cell Differentiation

    • Clonal selection means that an antigen is presented to many circulating naive B and (via MHC) T cells, and that the lymphocytes that match the antigen are "selected" to form clones of themselves, both memory and effector.
    • T Cell differentiation happens via the following steps:
    • Cloned daughter cells differentiate into either effector T cells or memory T cells.
    • Cytotoxic effector T cells are finished, but helper T cells continue to differentiate into individual subsets of helper T cells.
    • Clonal selection of lymphocytes: 1) A hematopoietic stem cell undergoes differentiation and genetic rearrangement to produce 2) immature lymphocytes with many different antigen receptors.