T Cells


  • T cells contribute to the immune defenses in two major ways

  Regulatory T cells are vital to orchestrating the elaborate system. (B cells, for instance, cannot make antibody against most substances without T cell help).
  Cytotoxic T cells, on the other hand, directly attack body cells that are infected or malignant.
  • Most important regulatory T cell is the "helper/inducer" cell. Helper T cells are essential for activating B cells and other T cells as well as natural killer cells and macrophages.
  • Another subset of T cells acts to turn off or "suppress" these cells.
  • Cytotoxic T cells, are killer cells. In addition to ridding the body of cells that have been infected by viruses or transformed by cancer, they are responsible for the rejection of tissue and organ grafts.
  • T cells work primarily by secreting substances known as cytokines or, more specifically, lymphokines. Lymphokines are diverse and potent chemical messengers. Binding to specific receptors on target cells, lymphokines call into play many other cells and substances, including the elements of the inflammatory response. They encourage cell growth, promote cell activation, direct cellular traffic, destroy target cells, and incite macrophages.
  • One of the first cytokines to be discovered was interferon - a family of proteins with antiviral properties.
  • Natural Killer (NK) cells are yet another type of lethal lymphocyte. Unlike cytotoxic T cells, they do not need to recognize a specific antigen before swinging into action. They target tumor cells and protect against a wide variety of infectious microbes. In several immunodeficiency diseases, including AIDS, natural killer cell function is abnormal