to have a direct function as PRRs in the recognition of peptidoglycan (PGN)derived peptides. NOD1 senses γ-D-glutamyl-meso-diaminopimelic acid (that is,-DAP) that is derived from Gramnegative bacteria (34) , whereas NOD2 senses muramyl dipeptide, which is from both Gram-positive and Gram-negative bacteria (35, 36) . When NODs bind with PGN-derived peptides, they rapidly form oligomers, which lead to the recruitment of the receptor-interacting protein 2 (RIP2) kinase through CARD-CARD interactions (37) . This complex of NOD1-RIP2 or NOD2-RIP2 then recruits the inhibitor of NK-κB kinase complex (IKK), leading to the activation of NF-κB. Activation NOD1 and NOD2 can also initiate an MAPK pathway that leads to the activation of p38 and ERK. In addition, NOD1 signaling can activate JNK as well (38) . NALP proteins are characterized by the presence of an N-terminal pyrin effector domain (39) . Several NLRs, namely NALP1, NALP2 and NALP3, have an important role in activation of proinflammatory caspases through formation of inflammasome (37, 40) . The inflammasome is a multiprotein complex of more than 700 kDa that is responsible for the activation of caspases 1 and 5, leading to the processing and secretion of the proinflammatory cytokines IL-1β and IL-18 (41, 42) . Martinon et al. have presented different caspase activation platforms in which different components constitute the various inflammasomes (43) . Two types of NALP inflammasome are better studied: the NALP1 inflammasome that is composed of NALP1, the adaptor protein ASC, caspase-1 and caspase-5 (41) , and the NALP2/NALP3 inflammasome that contains NALP2 or NALP3 CARDI-NAL, ASC and caspase-1 (44) .