Solitary Intestinal Lymphoid Tissue Provides a Productive Port of Entry for Salmonella enterica Serovar Typhimurium

Abstract

Oral infection of mice with Salmonella enterica serovar Typhimurium results in the colonization of Peyer's patches, triggering a vigorous inflammatory response and immunopathology at these sites. Here we demonstrate that in parallel to Peyer's patches a strong inflammatory response occurs in the intestine, resulting in the appearance of numerous inflammatory foci in the intestinal mucosa. These foci surround small lymphoid cell clusters termed solitary intestinal lymphoid tissue (SILT). Salmonella can be observed inside SILT at early stages of infection, and the number of infected structures matches the number of inflammatory foci arising at later time points. Infection leads to enlargement and morphological destruction of SILT but does not trigger de novo formation of lymphoid tissue. In conclusion, SILT, a lymphoid compartment mostly neglected in earlier studies, represents a major site for Salmonella invasion and ensuing mucosal pathology.

Development of Secondary Lymphoid Organs

“…These data argue that the location and number of ILFs is determined developmentally and cannot be altered by inflammation or infection. However, the final maturation and organization of ILFs is dependent on microbial stimuli and can even be enhanced by infection with pathogenic bacteria (128). Together, these data demonstrate that the development of ILFs has some characteristics in common with the development of ectopic lymphoid follicles, but other characteristics of secondary lymphoid organs.…”

Delivery strategies to enhance oral vaccination against enteric infections

“…As in the case of PPs, a follicle associated epithelium with M cells is present on the lumen facing side of ILFs. Uptake of pathogens including S. typhimurium, leads to the formation of germinal centers (GCs) in mature ILFs [64][65][66]. Interestingly, it was found that the presence or absence of GCs in ILFs did not influence the active class switching of naïve B cells to active IgA secreting B cells [67].…”

Dissemination of Persistent Intestinal Bacteria via the Mesenteric Lymph Nodes Causes Typhoid Relapse

“…Therefore, Salmonella most likely persists at another gastrointestinal site, which we could not detect even by sensitive culture methods. One potential site would be solitary intestinal lymphoid tissues (SILT), poorly studied lymphoid cell clusters that are known to be infected with Salmonella following oral infection (18). Such a low level of persistence is more rapidly manifested in adenectomized mice, which lack the protective firewall of the MLNs to reduce the systemic spread of bacteria after the removal of antibiotics.…”