The immune system is an intricate and fascinating network of many different cell types and signaling molecules that work together to protect the human body against foreign pathogens.
T cells are responsible for regulating the immune response, and much like a motley crew, they possess diverse backgrounds due to exposure to many different pathogens. It is this diversity, in part, which makes them such powerful regulators of the immune system.
However, T cells are more of an orchestrated motley crew – they consist of a diverse and seemingly unstructured set of cells, which are involved in an incredibly intricate and organized dance between destruction of foreign bodies and preservation of host cells.
Let’s explore that dance a little further. When you are exposed to a foreign pathogen, influenza virus for example, an antigen presenting cell (APC) such as a dendritic cell, will process and present viral antigens to your naïve CD4+ helper T cells.
The presentation of antigen serves to activate the T cell and stimulate it to secrete various cytokines and express specialized cell surface receptors. The specialized cell surface markers and cytokines will activate macrophages to destroy influenza, stimulate B cells to produce influenza specific antibodies, as well as maintain a steady level of self-tolerance to avoid destruction of your own cells and tissues.
The many roles just described are performed by a number of different subsets of CD4+ T cells, described in the table below.