NRP1 and gram-negative bacterial infections: Following gram-negative bacterial infection, DAP-type peptidoglycans from gram-negative bacteria are recognised by the peptidoglycan receptors PGRP- LC (a transmembrane receptor) and PGRP-LE (a secreted isoform and an intracellular isoform), which then activate the IMD intracellular signalling cascade [36,38].