Lymphatic capillaries have overlapping endothelial cells that act as one-way valves. Regarding pathogens, what is the importance of valves in immune function?

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Valves in lymphatic capillaries create a unidirectional path for interstitial fluid, including any pathogens it carries, toward lymph nodes. The overlapping endothelial cells act like one-way flaps: when tissue pressure pushes fluid in, the flaps open to admit it, but internal lymphatic pressure and surrounding tissue pulsations cause them to close and prevent fluid from flowing backward into the tissue. This backflow prevention is essential for immune function because it ensures pathogens and antigen-presenting cells are reliably delivered to lymph nodes for detection by immune cells. The flow is driven mainly by external forces like muscle movement and vessel dynamics, not by the valves themselves, and the valves do not block leukocyte entry into tissues.