Multiple Modes of Action of Anti-TNF-α Antibodies for Inflammatory Bowel Diseases Beyond TNF-α Neutralization

Inflammatory bowel diseases (IBDs), chronic inflammatory disorders of the gastrointestinal tract, are classified into Crohn's disease (CD) and ulcerative colitis (UC). Despite differing clinical manifestations, both CD and UC share a common immunopathogenesis, involving excessive production of proinflammatory cytokines by macrophages and dendritic cells. Tumor necrosis factor-α (TNF-α), interleukin-12 (IL-12), and IL-23 are prototypical proinflammatory cytokines associated with CD and UC development, and biologics targeting these cytokines are widely used for treating patients with IBD. Antibodies (Abs) against IL-12 and IL-23 decrease intestinal inflammation by binding to the soluble forms of IL-12 and IL-23, respectively. Notably, anti-TNF-α Abs induce remission by neutralizing soluble TNF-α as well as membrane-bound TNF-α (mTNF-α). The binding of anti-TNF-α Abs to mTNF-α enables the diverse functions of IBD-specific TNF-α-inhibitors. Multiple modes of action of anti-TNF-α Abs for IBD include complement-dependent cytotoxicity, Ab-dependent cellular cytotoxicity, apoptosis of cells expressing mTNF-α, apoptosis of lamina propria T cells, and induction of regulatory T cells and macrophages. In this article, we introduce the diverse actions of anti-TNF-α Abs beyond TNF-α neutralization and discuss how these unique properties of anti-TNF-α Abs contribute to the efficient downregulation of IBD-associated inflammation.