Figure 1.

A journey of GI microbes in the host. Epithelium is the gateway for the introduction of GI microbes inside the host and subsequent progression of GI diseases. Once microbes get through the gateway, the process of phagocytosis is initiated, and macrophages are the first line of defense. In macrophages, invading microbes are engulfed by phagocytosis into phagosomal structures and encounter a complex and dynamic range of host defenses. The recognition of bacterial antigens by a range of pattern recognition receptors expressed by macrophages triggers a signaling cascade leading to the recruitment of a diverse cell type complement including neutrophils, dendritic cells, natural killer cells, T lymphocytes and B lymphocytes.