T Cell Response (Edexcel A (SNAB) A Level Biology)

• T cells, sometimes known as T lymphocytes, are a type of white blood cell involved with the specific immune response
  • They are produced in the bone marrow and finish maturing in the thymus, which is where the T in their name comes from
• Mature T cells have specific cell surface receptors called T cell receptors
• These receptors have a similar structure to antibodies and are each specific to a particular type of antigen

 Mature T cells have many different types of receptor on the cell surface membrane; these receptors will bind to different antigens on antigen presenting cells

• T cells are activated when they encounter and bind to their specific antigen on the surface of an antigen presenting cell 
  • This antigen-presenting cell might be a macrophage, an infected body cell, or the pathogen itself
• These activated T cells divide by mitosis to increase in number
  • Dividing by mitosis produces genetically identical cells, or clones, so all of the daughter cells will have the same type of T cell receptor on their surface 
• As they divide by mitosis the T cells differentiate into three main types of T cell
  • T helper cells
    • Release chemical signalling molecules that help to activate B cells
  • T killer cells
    • Bind to and destroy infected cells displaying the relevant specific antigen
  • T memory cells
    • Remain in the blood and enable a faster specific immune response if the same pathogen is encountered again in the future