Abstract: The invention describes peptide, and proteins and fusion proteins comprising the peptides, that are capable of increasing the proliferation of cells, especially epithelial cells in the mammalian gastrointestinal tract. The peptides comprise the hydrophilic domain of the TadE subunit of the Tad pilus of Bifidobacterium, especially the pilus encoded by the Tad2003 gene cluster identified in Bifidobacterium breve UCC2003, and functional fragments of the hydrophilic domain. The invention informs new treatments for diseases and conditions that involve attenuated epithelial cell proliferation and growth, such as inflammatory conditions of the gastrointestinal tract and trauma of the skin including burns and other wounds. The invention also informs treatments of newborn babies to promote proliferation and growth of gut epithelial tissue by administration of agents comprising the peptide of the invention in the form of infant formula.