Surfactants like particles (SLP) are secreted by Intestinal epithelium. These particles have the ability to lower surface tension of intestinal epithelial cells and contain small amounts of surfactant specific proteins A, B, and D. In the intestinal lumen they are known to function as lubricants and/or as a vehicle to deliver digestive enzymes to the luminal fluid. These particles have been found to have the ability in binding of uropathogenic E.coli. But their immunological function is not known. The present study was designed to assess the role of the SLP in the regulation of immune response during Salmonella (S) typhimurium infection using a rat an enteric model. The animals were divided in four different groups including control (PBS), rats fed fat diet (corn oil), rats fed fat diet followed with S. typhimurium infection and rats with S. typhimurium infection alone. The Peyer's patches (PP), intraepithelial (IE) and lamina propria (LP) mononuclear cells were isolated from the above-mentioned groups. These mononuclear cells were then incubated in presence of S. typhimurium lysate alone, SLP alone and S. typhimurium lysate and SLP together. T cell markers CD4 and CD8, cytokines mainly pro-inflammatory ones including IFN-γ, TNF-α, IL-12 etc were studied under such conditions. In addition histological studies were also carried out under these conditions. We report in this study that SLP plays an important role in modulating the cytokine level during infection. The pro-inflammatory cytokines were found significantly reduced in SLP induced diet along with the infection group compared to the infection group alone. Histopathological studies revealed the breakdown of duodenal villi after infection while only broadening of villi was observed in rats given corn oil induced SLP along with infection. These results suggested an important immuno-modulatory role for SLP during Salmonella infection.

Interaction between the enteric pathogen Salmonella typhimurium and the luminal surface of the intestine provoke an acute inflammatory response mediated in part by various inflammatory molecules. Surfactant‐like particles (SLP) are known to cover the surface of the intestinal epithelium, act as lubricants and/or as a vehicle to deliver digestive enzymes to the luminal fluid. Recently we have shown that SLP plays an important protective role during microbial insult. The data suggested that SLP‐induced diet prevents the damage of intestinal villi caused by S. typhimurium infection. The present study was designed to assess the role of SLP on secondary signaling molecules during S. typhimurium infection. The Peyer's patch, intraepithelial and lamina propria mononuclear cells were analyzed under various conditions for secondary signaling molecules, including calcium, inositol triphosphate and protein kinase C. SLP‐induced diet along with infection showed significant variation in these secondary signaling molecules, particularly in Peyer's patches, as compared to infection group alone. In addition, the cells isolated from the infected group upon incubation in vitro with SLP also showed a considerable variation of these molecules. These results suggested an important influence of SLP on secondary signaling molecules and, in turn, could be important in overall immune modulation during infection. PRACTICAL APPLICATIONS Salmonella are known to cause disease in humans, animals and birds worldwide. Over 1.4 million cases of salmonellosis (gastroenteritis) per year occur in the U.S.A. and other industrialized countries. Countries with poor sanitation have a much higher incidence of salmonellosis. The disruption of epithelial barrier integrity by Salmonella has pathological consequences. Intestinal epithelium secretes surfactant‐like particles (SLP); these particles have the ability to cover the surface of the cell in the intestinal lumen. They are known to have ability in binding of uropathogenic Escherichia coli and in protecting the disruption of intestinal villi. The present study provides further evidence for its role in regulating secondary signaling molecules and overall immune response. SLP induced by dietary fat enhanced the resistance to intestinal infections, as it possibly decreases the colonization and translocation of S. typhimurium. The SLP and microbe interaction may thus represent a delicate balance between symbiosis and pathogenesis.