Varying blood monocyte and dendritic cell responses after laparoscopic versus open gastric bypass surgery

Laparoscopy may activate innate immunity less than conventional open surgery. This may be important in obese patients who have pre-existing low-grade inflammation. This study examined phenotypic changes in blood monocytes (Mcs) and dendritic cells (DCs) from patients undergoing laparoscopic (L) or open (O) Roux-en-Y gastric bypass (RYGBP) surgery.

8 patients (3 male) had blood drawn before and after RYGBP, and on postoperative day (POD) 1, 3, and 28. Mc and DC quantity, phenotype, and activation status were determined by flow cytometry.

Mean BMI was 53 +/- 4 and 46 +/- 1, and length of stay was 6.3 +/- 3.2 and 3.5 +/- 0.6 days, in the O (n=4) versus L (n=4) groups, respectively. Postoperative WBC count was 16 +/- 1 x 10(3)/mm3 after O and 10 +/- 1 x 10(3)/mm3 after LRYGBP (P<0.001). This was due to a greater rise in neutrophils and decline in lymphocytes after ORYGBP (P<0.001). Total Mcs increased in both groups at POD 1, but the number of CD18+ Mcs was reduced after ORYGBP (P=0.04). Mc human leukocyte antigen (HLA)-DR expression was lower in CD16+ Mcs after ORYGBP, suggesting decreased capacity to present antigen (P=0.002). Postoperatively, total DCs decreased in both groups, but recovered (P=0.04). The proportion and activation of the tolerogenic DC2 phenotype was lower, whereas the percentage of the ldDC phenotype was higher, in the O group (P=0.006).

RYGBP changes the quantity and phenotype of circulating blood Mcs and DCs. Although there were overall similarities in the overall response to gastric surgery between open and laparoscopic, there were some notable differences, including a greater reduction in HLA-DR expression and increased number of immature DCs in the ORYGBP group. The findings suggest that RYGBP may have varying immunologic consequences depending upon the surgical procedure employed.