NRP1 and chronic obstructive pulmonary disease: As LTi ILC3s crucially contribute to the formation of ectopic lymphoid aggregates via the secretion of lymphotoxin, IL-17A, and IL-22 (223), it was interesting to find a significantly increased number of neuropilin-1 (NRP1)-positive LTi cells in pulmonary tissue of COPD patients (224).