Bacterial lipopolysaccharide (LPS) is present in the outer membrane of Gram-negative bacteria and functions as pathogen-associated molecular pattern (PAMP) (Whitfield and Trent, 2014). LPS therefore is a potent activator of inflammatory responses leading to cytokine release and neutrophils recruitment. The lipid A moiety of LPS activates the complex consisting of the LPS binding protein (LBP), CD14, MD-2 and Toll-like receptor 4 (TLR4) and the non-canonical inflammasome-linked caspases-4, 5 and 11, which in turn activate the canonical NLRP3 inflammasome (Shi et al., 2014; Hagar et al., 2013; Kayagaki et al., 2013; Hoshino et al., 1999; Poltorak, 1998; Nagai et al., 2002; Park et al., 2009; Ratsimandresy et al., 2013). In particular, the cytokine interleukin (IL)-1β produced in response to inflammasome activation has a crucial role in neutrophil recruitment through promoting neutrophil adhesion and migration (McDonald et al., 2010).This protocol allows studying of inflammatory response induced by LPS that affect neutrophil infiltration by tracking myeloperoxidase (MPO) activity in vivo (de Almeida et al., 2015).

In response to pathogen infection and tissue damage, inflammasome sensors such as NLRP3 and AIM2 are activated, which triggers PYRIN domain (PYD)-mediated ASC nucleation, followed by self-perpetuating ASC polymerization, which ultimately culminates in caspase-1 activation, interleukin (IL)-1β and IL-18 processing and release and pyroptosis (Ratsimandresy et al., 2013; Cai et al., 2014). Inflammasomes release not only cytokines, but also the polymeric ASC danger particles (pASC) by pyroptosis, which perpetuate and propagate inflammasome responses to bystander cells to engage cell intrinsic ASC and caspase-1 (Baroja-Mazo et al., 2014; Franklin et al., 2014). In this protocol we describe intraperitoneal injection of polymeric ASC particles as a danger signal and measure neutrophil infiltration and levels of the pro-inflammatory cytokine IL-1β by ELISA in the peritoneal lavage (de Almeida et al., 2015).