Minimally invasive versus open Roux-en-Y gastric bypass: effect on immune effector cells

Minimally invasive surgery (MIS) has several potential benefits compared with the open approach, including potentially less perioperative immunosuppression. Data characterizing the differential stress responses have been limited to serum cytokine analyses and animal studies. We hypothesized that the open approach to Roux-en-Y gastric bypass (RYGB) has a more deleterious, negative, quantifiable effect on the peripheral blood mononuclear cells than does the MIS approach.

Patients undergoing open and MIS RYGB for morbid obesity had blood samples collected preoperatively and postoperatively on days 1 and 2 and at the first follow-up visit. The peripheral blood mononuclear cells were isolated and analyzed for phenotype using flow cytometry, natural killer cell cytotoxicity using 51-chromium release assay, and gene expression using Affymetrix U133 Plus 2.0 microarray.

Patient age and body mass index were similar between the 2 groups. Postoperatively, differences within the open group were seen for CD3+/CD16- (T lymphocytes), CD3-/CD16+ (natural killer cells), CD3+/CD4+ (T-helper lymphocytes), and CD4/CD8 subsets (P<.05). No differences were seen within the open group CD3+/CD8+ (cytotoxic T lymphocytes) or within the MIS subsets. Between the 2 approaches, no phenotypic differences were found, except for the postoperative day 1 CD3+/CD16- (P<.05). Within each group, significant decreases were found in cytotoxicity on days 1 and 2 compared with preoperatively (P<.05). The cytotoxicity seen after MIS had returned to the preoperative levels at the first follow-up visit, but the cytotoxicity after open RYGB had not (P<.05). Between the 2 groups, the open group had greater cytotoxic decreases than did the MIS group at postoperative days 1 and 2 (P<.05). Microarray analysis of the preoperative (n=20) and day 2 (n=20) specimens identified a 20-gene signature that correlated with the surgical approach.

Open RYGB surgery causes greater inhibition of innate immunity than does MIS. This inhibition was not accounted for by phenotypic changes. Gene expression changes from surgical stress might represent the molecular basis of this differential immune response.