We previously characterized conservation and divergence in Toll-like Receptor (TLR)4-dependent transcriptional responses in human versus mouse macrophages. In this study, we focused on orthologous human and mouse genes uniquely regulated by lipopolysaccharide (LPS) in primary human macrophages. We confirmed “human-specific” LPS regulation of these genes by examining expression in primary human macrophages versus a panel of different mouse macrophage populations. In investigating potential functions, we found that one of these genes (a novel ubiquitin ligase) was required for NLRP3 inflammasome responses, as demonstrated by gene knock-down in both primary human macrophages and PMA-differentiated THP-1 cells. The NLRP3 inflammasome is a multi-protein complex containing NLRP3, ASC and caspase-1. Activation of the NLRP3 inflammasome results in the processing and release of the pro-inflammatory cytokines IL-1beta and IL-18, as well as pyroptotic cell death. NLRP3 assembly requires both a priming signal such as that delivered by the TLR4 agonist LPS, as well as a triggering signal such as damage-associated host molecules (e.g. ATP) or pathogen-associated stimuli. Recent studies have demonstrated that direct deubiquitination of NLRP3 is required for triggering of the NLRP3 inflammasome. Our findings now suggest that one of the mechanisms by which LPS primes inflammasome responses in human macrophages is via the upregulation of a specific ubiquitin ligase. We provide evidence that this ubiquitin ligase affects LPS priming of inflammasomes in human macrophages by promoting ubiquitination-dependent degradation of p21(Waf1/Cip1), which has previously been shown to inhibit LPS-inducible IL-1beta expression independently of its cell-cycle inhibitory role. Current studies are aimed at further exploring the dynamics of p21 protein regulation by the ubiquitin ligase, as well as p21 regulation of IL-1beta synthesis. These findings provide new insights into mechanisms affecting pathological inflammatory processes and provide direction for potential treatment strategies.