NRP1 and periodontal disorder: The triggering receptor expressed on myeloid cells 1 (TREM-1) is an immunoglobulin superfamily transmembrane receptor found mostly on neutrophils, monocytes, and macrophages. TREM-1 triggers and amplifies inflammatory immune responses by interacting with Toll-like receptor signaling. Recently TREM-1 has been suggested as a candidate marker for new treatment strategies against periodontal diseases.