Lymphocytes

The lymphocytes are a class of white blood cells considered to be part of the adaptive immune system. There are two major classes of lymphocytes:

Lymphocytes have evolved to provide a more versatile means of defense. These cells display on their cell surface receptors that recognize specific antigens. When activated, the cell enlarges to form a lymphoblast and then proliferates and differentiates into an antigen-specific effector cell.

 

cartoon of lymphocytes T cells CD4, CD8, Treg and B cells

T cells are named after the organ they develop in, the Thymus.

T cells are divided in different subsets and types depending on the receptors they express on the surface as well as their gene expression and function.

T helper cells, also known as CD4+ T Cells, organize and “help” to alert other cells to coordinate the immune system to clear pathogens (the bad guys). CD4 T cells are divided into various subsets such as T h1, Th2, Th17. Another subset of CD4 T cells includes regulatory T cells also known as suppressor T cells, which are shown in the cartoon above as the police CD4 T cells. Regulatory T cells (T regs) act like suppressor cells that control the immune system and promote tolerance. These cells make sure the immune response doesn’t get out of hand and I therefore think of them as little police officers controlling and ensuring there is order.

CD4 T cell Lymphocyte Cartoon Super hero


Cytotoxic T cells (CTLs), also known as Killer T cells,  are a special type of T cells with the ability to kill other cells. Usually they kill cells that have been infected with a virus. This way the virus can no longer use these cells for replicating inside of them. CTLs secrete cytotoxins to kill the other cells and are therefore called “cytotoxic” T cells.

 

CD8 CTL Killer T Cell Cartoon


 

B cells develop in the bone marrow and are therefore called B cells. These cells are responsible for producing antibodies. The antibodies produced by B cells circulate around our body and bind to specific viruses or bacteria to neutralize them and help get them killed by other cells of the immune system.
B cell Cartoon antibodies white background

 


References:

Immunobiology, 5th edition. The Immune System in Health and Disease
Authors: Charles A Janeway, Jr, Paul Travers, Mark Walport, and Mark J Shlomchik.