An investigation into the effect of a probiotic on gut immune function in surgical patients.

Background: The gut-associated lymphoid tissue (GALT) is an important component of the gut barrier. We have previously demonstrated a significant increase in various parameters of gut immune function in association with bacterial translocation. Animal studies have suggested that the probiotic Lactobacillus plantarum 299v improves the immunological status of the intestinal mucosa. The aim of this study was to determine whether the same is true in humans.

Method: This was a prospective randomised controlled study, in which immunohistochemical techniques were used to measure the concentrations of plasma cells, IgA positive cells and IgM positive cells in the lamina propria, together with the concentrations of IgA and IgM at the mucosal surface in specimens of normal small bowel obtained from patients undergoing elective abdominal surgery who had consumed an oral preparation containing the probiotic Lactobacillus plantarum 299v (ProViva) during the immediate preoperative period. These were compared with similar specimens obtained from control subjects who did not receive the probiotic.

Results: A total of 22 patients were studied (probiotic group n = 11, control group n = 11). The median volume of ProViva consumed was 3250 ml (range 2100-9000 ml), for a median duration of 9 days (range 5-18 days). There were no significant differences between the probiotic and control groups in terms of concentrations of plasma cells, IgA positive cells or IgM positive cells in the lamina propria. There was a significantly higher concentration of IgM at the mucosal surface in the control group (P = 0.02, Fishers Exact test mid P), but no difference in terms of IgA.

Conclusions: The increase in IgA observed in the intestinal mucosa in response to probiotics in animal studies does not occur in humans. The significance of the increase in IgM at the mucosal surface in the controls is unclear.