Pathogens that enter through the skin barrier can access draining lymph nodes via lymph fluid. In eLife, Cyster and colleagues identify a role for a population of non-circulating CCR6+ innate-like lymphocytes that protects the exterior surfaces of lymph nodes against lymph-borne pathogens. This population shows enrichment for Vγ4+ γδ T cells that can rapidly produce interleukin 17 upon bacterial or fungal challenge. The trafficking receptors S1PR1 and CCR6 are both required for proper positioning of these cells in or near the subcapsular sinus, where they can establish contact with subcapsular macrophages. The sialic-acid-binding lectin CD169 is essential for these cellular interactions and for the resistance of Vγ4+ γδ T cells to hydrodynamic lymph fluid flow to maintain their retention on surface of lymph nodes.