Lymphatic system primer

Lymph nodes are found throughout the body and are located on the lymphatic vessels at various intervals along the lymphatic routes.
During the process of circulating through the lymphatic system, lymph fluid accumulates antigens and other biomolecules captured from the tissues.
This fluid then drains into the lymph nodes, where it encounters T cells and B cells congregate together with Antigen Presenting Cells (APCs).

APCs and certain other immune cells contained in the lymph nodes function to constantly sample the lymph fluid searching for signs of potential threats within the body.
APCs serve as sentinels to orient the cells of the adaptive immune response to develop a properly targeted and functional protective response by presenting these cues to B cells, T cells, and other lymphocytes within the lymph nodes.

The activation of B cells and T cells with proper specificity and functionality marks the genesis of the adaptive immune response whereby numerous disease-specific and functionally-matured lymphocytes are expanded and deployed.
After sufficient interaction with APCs within the lymph nodes, these activated B cells and T cells exit the lymph nodes and eventually enter the bloodstream, which distributes them throughout the body to accumulate at disease sites.
Critically, signaling delivered between immune cells residing in the lymph nodes orchestrates the immune response to determine the magnitude, potency, persistence, functionality, specificity, and memory capacity of the developing response.

Lymphatic system diagram