Anti-inflammatory effects of infliximab in mice are independent of tumour necrosis factor α neutralization

Infliximab (IFX) has been used repeatedly in mouse preclinical models with associated claims that anti‐inflammatory effects are due to inhibition of mouse tumour necrosis factor (TNF)‐α. However, the mechanism of action in mice remains unclear. In this study, the binding specificity of IFX for mouse TNF‐α was investigated ex vivo using enzyme‐linked immunosorbent assay (ELISA), flow cytometry and Western blot. Infliximab (IFX) did not bind directly to soluble or membrane‐bound mouse TNF‐α nor did it have any effect on TNF‐α‐induced nuclear factor kappa B (NF‐κB) stimulation in mouse fibroblasts. The efficacy of IFX treatment was then investigated in vivo using a TNF‐α‐independent Trichuris muris‐induced infection model of chronic colitis. Infection provoked severe transmural colonic inflammation by day 35 post‐infection. Colonic pathology, macrophage phenotype and cell death were determined. As predicted from the in‐vitro data, in‐vivo treatment of T. muris‐infected mice with IFX had no effect on clinical outcome, nor did it affect macrophage cell phenotype or number. IFX enhanced apoptosis of colonic immune cells significantly, likely to be driven by a direct effect of the humanized antibody itself. We have demonstrated that although IFX does not bind directly to TNF‐α, observed anti‐inflammatory effects in other mouse models may be through host cell apoptosis. We suggest that more careful consideration of xenogeneic responses should be made when utilizing IFX in preclinical models.

An unusual diaphragmatic hernia with gastric perforation and sub-acute presentation

Gastric perforation into the thoracic cavity through a diaphragmatic hernia is rare but, when it occurs, patients present in severe distress, with mortality approaching 50%. We present a unique case in which a fibrotic reaction between the stomach and the parietal pleura led to a subacute presentation upon perforation. The extra time that this afforded led to more effective multidisciplinary team management and ultimately an excellent outcome for the patient.

NSAID-induced diaphragmatic disease of the colon

One of the rare side effects of chronic usage of non-steroidal anti-inflammatory drugs is colopathy, which is characterised by colonic inflammation, ulceration and formation of diaphragms in late stages. We treated a case of colonic diaphragm disease with similar findings in our unit recently. We present the case herewith, followed by a discussion of the management of this interesting rare but benign condition.

Lead shot incarceration in appendix: an unusual cause of appendicular foreign body

A previously fit man was investigated for right-sided abdominal pain and an appendicular foreign body (FB) caused by ingested lead shot was found. He had associated urinary tract infection causing his symptoms and hence was treated conservatively. We present this rare case, followed by discussion of the causes, investigations, clinical significance and management of appendicular FBs.

Arginase-1-expressing macrophages are dispensable for resistance to infection with the gastrointestinal helminth Trichuris muris

Alternatively activated macrophages (AAMs) have key roles in the immune response to a variety of gastrointestinal helminths such as Heligmosomoides bakeri and Nippostrongylus brasiliensis. In addition, AAMs have been implicated in the resolution of infection-induced pathology in Schistosoma mansoni infection. AAMs exert their activity in part via the enzyme arginase-1 (Arg1), which hydrolyses l-arginine into urea and ornithine, and can supply precursor substrate for proline and polyamine production. Trichuris muris is a worm that resides in the large intestine with resistance being characterized by a Th2 T-cell response, which drives alternatively activated macrophage production in the local environment of the infection. To investigate the role of AAMs in T. muris infection, we used independent genetic and pharmacologic models of arginase deficiency. In acute infection and Th2-dominated immunity, arginase-deficient models expelled worms normally. Macrophage-Arg1-deficient mice showed cytokine and antibody levels comparable to wild-type animals in acute and chronic infection. We also found no role for AAMs and Arg1 in infection-induced pathology in the response to T. muris in either chronic (Th1 dominated) or acute (Th2 dominated) infections. Our data demonstrate that, unlike other gastrointestinal helminths, Arg1 expression in AAMs is not essential for resistance to T. muris in effective resolution of helminth-induced inflammation.