Figure 3. The dermal lymphatic sits center stage for the drainage of immune-active cells.

Skin grafts, allergens, or immunization stimulate a variety of immune cells, including T cells, Langerhans cells, dendritic cells, and macrophages, which exit from the skin via the lymphatic system. Antigen-presenting cells cells exit the dermis via the lymphatic postcapillary venules and travel to the dermal lymphatic and then on to the lymph node, in which they activate and expand lymphocytes that secrete antibodies or otherwise target the antigen. Immune cells then travel through the lymphatic vasculature and enter the blood circulation via the thoracic duct. The blood is filtered through the spleen, which can lead to additional activation and expansion of antigen-targeted immune cells.