Hypersensitivities induced by silk knot at differential levels in murine abdominal wall

Objective Silk knot induced inflammatory response occurs after percutaneous extracorporeal knotting for laparoscopic inguinal inner ring closure in children. The present study was intended to explore the correlation between antigen-presenting cell (APC) and CD4+ Th cell infiltrations during knot-induced delayed hepersensitivity and differential knot locations in murine abdominal wall. Methods Three 0.5 cm-long vertical and parallel incisions in abdominal wall were created in the same Balb/C mice, followed by initialized stitch in the same path using MERSILK non-absorbable suture. The knots were located in subcutaneous, intramuscular and extra peritoneal space in abdominal wall. The knot segments in each group were harvested at Day 14 post-operation. Hematoxylin & eosin (H&E) and imunohistochemical (IHC) stains were employed for examining the location of knots in each group and determining the infiltration of APC/CD4+ Th cells. Results H&E staining indicated that knot was created accurately in subcutaneous, intramuscular and extra peritoneal space in abdominal wall. IHC stain indicated a less infiltration of APC and CD4+ Th cells in extra peritoneal space in abdominal wall. On the contrary, more could be noted in subcutaneous layer (0.89±0.06). Quantitative evaluation revealed that significant differences in APC infiltration existed between subcutaneous and intramuscular layer groups [2.23±0.31 vs. 1.67±0.12, P=0.043 9] and between intramuscular and extra peritoneal space groups (P=0.002 0). Regarding CD4+ Th cell infiltration, quantitative evaluations revealed that significant difference between subcutaneous and intramuscular layer groups [1.79±0.17 vs. 1.42±0.20, P=0.009 5] and between intramuscular layer and extra peritoneal space groups [0.51±0.15, P=0.002 8]. Conclusions Correlation exists between APC and CD4+ Th cell infiltrations during knot-induced delayed type hepersensitivity and differential knot locations in murine abdominal wall. Knot in extra peritoneal space induces milder hypersensitivity in abdominal wall than other subcutaneous and intramuscular layers. Therefore knot in extra peritoneal space is more prone to lower knot-induced hypersensitivity and inflammation. Knotting in extra peritoneal space contributes to fewer complications after laparoscopic inguinal inner ring closure in children. Key words: Abdominal wall; Knot; Depth; Immune response