TLR4 and gram-negative bacterial infections: Despite the prevailing belief that the Toll pathway is activated by Gram-positive bacteria and fungi, whereas the Imd pathway responds to Gram-negative bacterial infection (48, 58, 59), our data indicates that DAP-PG from Gram-negative bacteria can also trigger the autoactivation of ModSP in conjunction with PGRP-SA and GNBP1 (fig.