TNF and gout: However, when we gave HmgclS100a8-Cre mice intraperitoneal (ip) injections of monosodium urate crystals, the causative agent of gout and potent neutrophil stimulus, HMGCL-deficient neutrophils had similar migration into the peritoneal cavity, but there was an overall lower inflammatory response based on Il1b and Tnfa gene expression (Figs. 3, G–J and S1).