T Cells and Immunity - It's NOT just about antibodies!

10 November 2020

Much has been spoken and written recently about antibodies and how they determine our immunity. Whilst they do have a role, that is not the full story, as antibodies are just one branch or aspect of our Immune System. Little has been said about the critical roles of T Cells.


We have 3 types of Lymphocyte cells – T Cells, B Cells and natural killer cells. T Cells are unique in that they can recognise various types of specific antigens (substances that provoke an immune response). Unlike B Cells, T Cells do not utilise antibodies to fight germs.


I will try to outline the various functions of T Cells in a simplified manner, to demonstrate just how effective they are. They play a hugely important role in our Immune System.


There are several types of T cell lymphocytes, each with specific functions in the Immune System, which can get very technical, but simply put, the common T Cells include:


  1. Cytotoxic T Cells: These are involved in the direct destruction of cancerous or infected Cells. They attack foreign tissue – so can be a problem in transplanted organs.
  2. Helper T Cells: These guys precipitate the production of antibodies by B Cells and help to activate cytotoxic T Cells.
  3. Regulatory T Cells: Suppress the response of B Cells and other T Cells to antigens, so that the immune response is proportionate. Defects in this type can lead to autoimmune disease where immune Cells attack the body’s own tissue.
  4. Natural Killer T Cells (NKT): Known as NKT to avoid confusion with natural killer cells mentioned above, NKT Cells can distinguish infected or cancerous cells from normal body cells and attack any cells that do not contain molecular markers that identify them as body cells.
  5. Memory T Cells: These are very important when it comes to immunity! They help the Immune System to recognise previously encountered antigens and respond to them more quickly and for a longer period of time. Cytotoxic T Cells and Helper T Cells can become Memory T Cells. Memory T Cells are stored in the lymph nodes and spleen and provide lifetime protection against specific antigens in some cases.


Activation of T Cells is a chain of events. In simple terms, Cytokines signal the T Cell to destroy the specific antigen. The activated T Cell multiplies and differentiates into Helper T Cells, which initiate Cytotoxic T Cells and others to terminate the antigen.


Given all of the above, it is wrong to assume that we have lost immunity, just because our antibodies are lacking. The Immune System is much more than antibodies as the function of T Cells demonstrates.


SUMMARY

T Cells originate from bone marrow and mature in the thymus gland, in the lymphatic system.

T Cells are lymphocyte immune cells that protect the body against cancerous cells and cells that have become infected by pathogen, such as bacteria and viruses. Actually, the T in T Cells stands for Thymus derived.

Cytotoxic T Cells actively destroy infected cells.