PD-1/PD-L1 immune checkpoint pathway. PD-L1 is expressed on antigen-presenting cells whereas PD-1 is expressed on T-lymphocytes. The PD-1–PD-L1 pathway impairs the ability of T-lymphocytes to mount an immune response. This is a key checkpoint in a normal immune response.Abbreviation: APC, antigen-presenting cells. Update on benefit of immunotherapy and targeted therapy in melanoma: the changing landscape. Srivastava N, McDermott D - Cancer management and research (2014). Not Altered. CC.
The normal immune response is way the body defends itself against substances it sees as harmful or foreign. The immune system recognizes the antigens (usually proteins) on the surface of substances or microorganisms, and attacks and destroys, or tries to destroy, them.
Immunity is the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells.
