Delayed-type hypersensitivity response is better preserved in mice following insufflation than after laparotomy

Our laboratory has previously used pig and rat models to demonstrate that delayed-type hypersensitivity (DTH) response to an antigen challenge is suppressed following laparotomy compared to insufflation. The purpose of this study was to develop a practical and reliable mouse DTH model that could be used in future studies to test immunomodulating drugs and therapies.

Female C3H/HeN mice (n = 100) were given three serial DTH challenges of 25 microl of 4 mg/ml phytohemagglutinin (PHA) 12 days before the test procedure, immediately following the test procedure, and on the 2nd postoperative day. All challenges were administered via subcutaneous injection in alternating footpads. The thickness of the footpad was determined with electronic calipers immediately prior to injection and 24 h following injection in a blinded fashion. The difference in thickness represents the response. On the day of the procedure, mice were randomized into the following three groups: (a) control (AC), (b) insufflation (INS), and (c) open (OPEN). AC mice underwent no procedure. INS mice underwent CO(2) insufflation at 2-4 mmHg for 20 min. OPEN mice underwent a midline incision from xiphoid to pubis that was closed after 20 min. Data were analyzed using ANOVA and Tukey-Kramer tests to determine differences between groups.

Preoperatively, there were no significant differences among the three groups. On POD1, the OPEN group had significantly less response than both the AC and INS groups. On POD3, there were significant differences between the OPEN group and both the INS and AC groups. There was no significant difference between the AC and INS group at any time.

In conclusion, a DTH mouse model has been established that allows serial assessment of cell-mediated immune function. This model can be used to study immune function after open and minimal access procedures in a simple and cost-effective manner.