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T Lymphocytes: Helpers

  1. Izumi Kawachi1,
  2. Takayuki Kondo2

Published Online: 19 SEP 2013

DOI: 10.1002/9780470015902.a0001224.pub3

eLS

eLS

How to Cite

Kawachi, I. and Kondo, T. 2013. T Lymphocytes: Helpers. eLS. .

Author Information

  1. 1

    Brain Research Institute, Department of Neurology, Niigata University, Asahimachi 1, Chuo-ku, Niigata, Japan

  2. 2

    Kitano Hospital Medical Research Institute, Department of Neurology, Osaka, Ohgimachi, Kita-ku, Japan

Publication History

  1. Published Online: 19 SEP 2013

Abstract

Abstract

Helper T lymphocytes (TH) are major histocompatibility complex (MHC) class II restricted CD4+ T cells that can be divided into several subsets depending on their cytokine releasing patterns: T-helper 1 (TH1), TH2, TH17, T-follicular helper (TFH), forkhead box P3+ regulatory T (Treg) cells and the recently described TH9 and TH22 cells and others. TH1 cells activate infected macrophages for the destruction of intracellular pathogens. TH2 and TFH cells provide help to B cells for antibody production. TH17 cells enhance neutrophil response for extracellular pathogens. Treg cells actively suppress immune reactions and help prevent the development of autoimmunity during immune response. It was initially thought that each TH subset retained a stable phenotype with a distinct lineage and played a distinct role in host defense and autoimmunity. Considerable overlap and flexibility of cytokine production by CD4+ T cells is challenging earlier concepts.

Key Concepts:

  • Helper T lymphocytes (TH) are MHC class II restricted CD4+ T cells that can be divided into several subsets of cytokine releasing patterns: T-helper 1 (TH1), T-helper 2 (TH2), T-helper 17 (TH17), regulatory T (Treg), T-follicular helper (TFH) and others.

  • TH cell subsets express a distinct set of genes that encode hallmark cytokines and unique transcription factors.

  • IFN-γ, IL-4, IL-17, IL-10/TGF-β and IL-21 are the representative cytokines of TH1, TH2, TH17, Treg and TFH cells, respectively, and are often used as subtype markers.

  • TH1 cells play an important role in cellular immune functions such as delayed-type hypersensitivity or defense against intracellular organisms.

  • TH2 cells enhance antibody production by B cells.

  • TH17 cells are potent inducers of tissue inflammation in autoimmune diseases and confer protection against extracellular bacterial and fungal pathogens.

  • Treg cells consist of a heterogeneous class of cells that suppress T-cell activity and help prevent the development of autoimmunity during immune response.

  • TFH cells regulate the step-wise development of antigen-specific B cell immunity in B cell follicles of lymphoid tissues.

Keywords:

  • MHC class II;
  • CD4;
  • T-helper 1;
  • T-helper 2;
  • T-helper 17;
  • regulatory T;
  • T-follicular helper;
  • antibody production