cell-mediated immunity

(noun)

Adaptive immunity that is not controlled by antibodies and is instead mediated directly by immune cells themselves, most notably type 1 helper T cells and cytotoxic T-cells.

Related Terms

Examples of cell-mediated immunity in the following topics:

  • 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.
    • Cellular immunity is mediated by T lymphocytes, also called T cells.
    • This type of immunity promotes the destruction of microbes residing in phagocytes, or the killing of infected cells to eliminate reservoirs of infection.
    • Another class of T cells called regulatory T cells function to inhibit immune response and resolve inflammation.
    • Their major role is to shut down T cell-mediated immunity toward the end of an immune reaction.

  • Cell-Mediated Immunity

    • Cell-mediated immunity involves cytotoxic T cells recognizing infected cells and bringing about their destruction.
    • 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.
    • Cytotoxic T cells mediate one arm of the cellular immune response
    • A summary of how the humoral and cell-mediated immune responses are activated appears in .
    • Depending on the cytokines released, this activates either the humoral or the cell-mediated immune response.

  • Type IV (Delayed Cell-Mediated) Reactions

    • Cell-mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, natural killer cells (NK), antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.
    • Therefore in cell mediated immunity cytokines are not always present.
    • Cell-mediated immunity is directed primarily at microbes that survive in phagocytes and microbes that infect non-phagocytic cells.
    • Unlike the other types, it is not antibody mediated but rather is a type of cell-mediated response.
    • CD4+ T cells secrete IL-2 and interferon gamma, further inducing the release of other Th1 cytokines, thus mediating the immune response.

  • Types of Adaptive Immunity

    • The adaptive immune response is mediated by B and T cells and creates immunity memory.
    • There are two subdivisions of the adaptive immune system: cell-mediated immunity and humoral immunity.
    • Cell mediated immunity is controlled by type 1 helper T cells (Th1) and cytotoxic T cells.
    • Humoral immunity refers to the component of the adaptive immune response that is caused by B cells, antibodies, and type 2 helper T cells (Th2), as well as circulating mast cells and eosinophils to a lesser extent.
    • This binding will cause degranulation and release of inflammatory mediators that start an immune response against the antigen.

  • Lymphoid Cells

    • A lymphocyte is a type of white blood cell in the immune system.
    • T and B lymphocytes are the main forces of adaptive immunity, which includes cell-mediated and humoral immunity.
    • 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.
    • Cytoxic T cells cause much of the damage associated with cell-mediated hypersensitivity, autoimmune disorders, and organ transplant rejection.

  • Adaptive Immunity and the Immunoglobulin Superfamily

    • There are two types of adaptive immune responses: humoral immunity and cell-mediated immunity.
    • The interaction of antigens with membrane antibodies on naive B cells initiates B cell activation .
    • Members of the IgSF include cell surface antigen receptors, co-receptors, and co-stimulatory molecules of the immune system, molecules involved in antigen presentation to lymphocytes, cell adhesion molecules, certain cytokine receptors, and intracellular muscle proteins.
    • When a B cell encounters its triggering antigen, it gives rise to many large cells known as plasma cells.
    • Describe the role of immunoglobulins in the adaptive immune response, specifically in humoral immunity

  • Specific T-Cell Roles

    • The different categories of T cells are the basis for cell-mediated immune system activity.
    • Cytotoxic T cells recognize their antigen on pathogens through their T cell receptor, and will kill the pathogen through degranulation and cell-mediated apoptosis.
    • The secondary immune response mediated by memory T cells is much faster and more effective at eliminating pathogens compared to the initial immune response.
    • Their major role is to shut down T cell-mediated immunity toward the end of an immune reaction and to suppress auto-reactive T cells that escaped the process of negative selection in the thymus.
    • Natural killer T cells (NKT cells – not to be confused with natural killer cells) bridge the adaptive immune system with the innate immune system.

  • Hypersensitivity

    • Mediators: IgE and IgG4.
    • Cytotoxic Hypersensitivity (Type II) is an immune response to human cells with foreign antigens.
    • Mediators: IgG (complement).
    • Associated disorders: Contact dermatitis, Mantoux test, Chronic transplant rejection, Multiple sclerosis, T-cells VAutoimmune disease receptor mediated, Graves' disease,Myasthenia Gravis.
    • Mediators: IgM or IgG (complement).

  • Overview of Adaptive Immunity

    • The adaptive immune system is composed of highly-specialized systemic cells and processes that eliminate or prevent pathogenic growth.
    • The adaptive immune system, also known as the specific immune system, is composed of highly-specialized systemic cells and processes that eliminate or prevent pathogenic growth.
    • Active immunity is generally long-term and can be acquired by infection followed by B cells and T cells activation, or artificially acquired by vaccines in a process called immunization.
    • In these cases, memory cells form for an antigen that elicits an immune response without actually being caused by a pathogen, which leads to immune system mediated-damage to the body from mast cell, antibody, or T-cell mediated activities and inflammation.
    • Helper T cells, or Th cells, coordinate immune responses by communicating with other cells.

  • Active and Passive Humoral Immunity

    • The humoral immune response is the aspect of immunity that is mediated by secreted antibodies.
    • The humoral immune response (HIR) is the aspect of immunity that is mediated by secreted antibodies produced by B cells.
    • Natural active immunity generally occurs as a result of infection with a pathogen, in which memory cells that remember the antigen of the infectious agent remain in the body.
    • Unlike active immunity, passive immunity is short lived (often only for a few month), because it does not involve the production and upkeep of memory cells.
    • Maternal passive immunity is a type of naturally acquired passive immunity, and refers to antibody-mediated immunity conveyed to a fetus by its mother during pregnancy.