PGRP-S is present in PMNs in tertiary (gelatinase) granules. Lysates of bone marrow PMNs or their isolated granules were separated by SDS-PAGE, and PGRP-S protein was detected on Western blots. The following granule markers were also detected: myeloperoxidase (MPO) for primary (azurophil) granules, lactoferrin for secondary (specific) granules, and matrix metalloproteinase 9 (MMP-9 or gelatinase B) for tertiary (gelatinase) granules. The results are from 1 of 4 similar experiments.