A C. jejuni deletion mutant lacking HtrA was shown to induce lower levels of apoptosis and reduced secretion of the pro-inflammatory cytokines monocyte chemoattractant protein (MCP)-1, interleukin (IL)-6, tumour necrosis factor (TNF)-α, and interferon (IFN)-γ in a mouse infection model, underscoring the protease's role in the bacterium's virulence (32). Here, TNF is linked to infection.