..., where the microbial burden is high, a mucus barrier forms the first line of defense by keeping bacteria away from the epithelial cells. In the small intestine where the mucus layer is less organized, microbes are kept at bay by peristalsis and antimicrobial peptides. Additionally, a dense glycocalyx...

...Roberta Martinelli; Adam S. Zeiger; Matthew Whitfield; Tracey E. Sciuto; Ann Dvorak; Krystyn J. Van Vliet; John Greenwood; Christopher V. Carman ABSTRACT Immune cell trafficking requires the frequent breaching of the endothelial barrier either directly through individual cells (‘transcellular...

...Le Shen; Eric D. Black; Edwina D. Witkowski; Wayne I. Lencer; Vince Guerriero; Eveline E. Schneeberger; Jerrold R. Turner Epithelial tight junctions form a barrier against passive paracellular flux. This barrier is regulated by complex physiologic and pathophysiologic signals that acutely fine-tune...

...Peter R. Cook In eukaryotes, motifs such as silencers, enhancers and locus control regions act over thousands of base pairs to regulate adjacent genes; insulators limit such effects, and barriers confine repressive heterochromatin to particular chromosomal segments. Recent results show that many...