Major abdominal surgery causes changes in lymphocyte subpopulations and impairs the immune response. Early enteral nutrition (EEN) enriched with probiotic bacteria may reduce this phenomenon and may improve the clinical course of this patients. The aim of this randomised, double-blind trial was to investigate changes of lymphocyte subpopulations of patients receiving EEN either enriched with lactic acid bacterium (LAB) or placebo before and after major abdominal surgery.

Thirty-three patients undergoing either pylorus-preserving pancreaticoduode-nectomy or Whipple's operation were enrolled. EEN enriched with either LAB (n = 17) or placebo (n = 16) was supplied for a period of 5 days beginning on the day before surgery. Blood samples were taken before surgery as well as postoperatively on day 1, 4 and 8. Flow cytometry analysis was performed immediately.

Numbers of total lymphocytes as well as T-helper (T4)-, T-suppressor (T8)- and natural-killer-lymphocytes decreased significantly in both groups. No significant differences in this parameters could be found between the groups. However, the T4/T8 ratio showed a higher increase from day 1 until day 8 in the verum-group. Simultaneously, mean expression of CD45RA on T4 cells was significantly lower in the verum-group while mean expression of CD45RO on T8 cells was significantly higher in this group.

Enrichment of EEN with LAB seems to have no significant influence on the well known postoperative decrease of total lymphocytes and natural-killer cells. In contrast, LAB supply seems to improve the T4/T8 ratio by mobilisation of mature T4 and T8 cells. Further investigations are necessary to evaluate the underlying mechanisms and clinical consequences.