Systemic activation and vascular infiltration of neutrophils with term labor.

Objective: The purpose of the current study was to determine if neutrophils infiltrate maternal systemic vascular tissue at the time of term labor.

Methods: Subcutaneous fat biopsies were obtained at cesarean delivery or abdominal surgery from laboring women (n = 5), non-laboring women (n = 5), and normal non-pregnant women (n = 5). Immunohistochemical staining was performed for CD66b, a neutrophil antigen, and intercellular adhesion molecule-1 (ICAM-1; CD54), an endothelial cell adhesion molecule for neutrophils. Vessels (10 to 200 microm) were analyzed for intensity of staining and percentage of vessels with staining.

Results: CD66b staining intensity was significantly greater for laboring women at term than for non-laboring women at term or for normal non-pregnant women (1.3 +/- 0.3 versus 0.2 +/- 0.1 versus 0.2 +/- 0.1, respectively, P < .01). Laboring women had significantly more vessels with staining for CD66b (79 +/- 4 versus 24 +/- 8 versus 19 +/- 6%, P < .001), more vessels with neutrophils adhered and flattened to endothelium (67 +/- 3 versus 16 +/- 7 versus 12 +/- 4%, P < .001), more vessels with neutrophils in the intima (30 +/- 6 versus 5 +/- 2 versus 2 +/- 1%, P < .05), and a greater number of neutrophils per vessel (5.4 +/- 1.1 versus 1.7 +/- 0.5 versus 1.2 +/- 0.3, P < .01) as compared to non-laboring or normal non-pregnant women. ICAM-1 staining was present in the endothelium of all groups, with no difference in staining intensity or percent of vessels stained. Between 86% to 96% of vessels stained for ICAM-1. Laboring patients had numerous leukocytes stained for ICAM-1 in their vessels.

Conclusion: This study demonstrates that neutrophils infiltrate maternal systemic vascular tissue at the time of term labor. Neutrophils were flattened and adhered to endothelium and infiltrated into the intimal space.