Anti-CD3 mAb Induced Necrotizing Enterocolitis in Formula-Fed Neonatal Mice through a Gut Microbiome Colonization Dependent Mechanism.

Necrotizing enterocolitis (NEC) is a serious disease that affects the small intestine of premature infants. Previous studies showed that formula feeding is a risk factor for NEC. Furthermore, gut microbiome and T cells are revealed to play a critical role in the pathogenesis of NEC. It has been reported that anti-CD3 mAb induces T cell activation and small intestinal injury in adult mice. However, how the small intestine of neonatal mice responses to anti-CD3 mAb treatment is uncertain. In the present study, we aimed to study the susceptibility of dam-fed and formula-fed neonatal mice to the anti-CD3 mAb challenge. For this purpose, mouse pups (P0) were nursed by dam feeding (DF) and formula feeding (FF) respectively. On postnatal day 2, pups were subjected to subcutaneous treatment with 10 mg/kg anti-CD3ε mAb. They were processed to measure intestinal permeability to FITC-dextran and euthanized at 24 h after administration of anti-CD3 mAb. Histology examination showed that FF but not DF pups developed NEC-like injury in the small intestine after anti-CD3 treatment. FF Pups were noted to display an increase in mortality, intestinal permeability, and inflammatory mediators upon anti-CD3 mAb challenge compared to DF pups. Even though the inflammatory markers were increased, the intestinal mucosa in DF pups remains intact after being challenged with anti-CD3. Remarkably, disruption of postnatal colonization by gavaging streptomycin attenuated NEC incidence in anti-CD3 mAb-treated FF pups, suggesting that bacterial colonization plays a role in predisposition of mouse pups by formula feeding to anti-CD3 mAb-induced intestinal injury. Taken together, this study provided the first evidence that anti-CD3 mAb induces NEC-like injury in neonatal mice receiving FF but not in DF via a microbiome colonization dependent manner. The underlying mechanisms regarding this pathophysiological event are to be studied in the future.