Dynamics and function of solitary intestinal lymphoid tissue.

Peyer's patches are the most prominent organized lymphoid tissue in the intestine and are generally considered to serve as an anatomical platform for the efficient induction of intestinal immune responses. However, besides Peyer's patches, phenotypically diverse, small-sized lymphoid structures are present, which mostly based on their phenotypical differences, have been assigned different names and putative functions. We have recently challenged this view and suggested that these structures represent different manifestations of the very same type of tissue, which we have termed solitary intestinal lymphoid tissue (SILT). A particular hallmark of SILT is its enormous plasticity, reflecting environmental stimuli such as the intestinal microflora. The functional role of SILT has largely been ignored for many years. However, recent reports indicate that SILT serves as port of entry for intestinal antigens and enteropathogens and is involved in the induction of intestinal immune responses. This review focuses on illuminating the concept of SILT and discusses its putative role in mucosal immune responses.