Fractalkine (FRK) levels in amniotic fluid and its production during pregnancy

Fractalkine is a new CX(3)C chemokine that has chemoattractant activity for T cells, monocytes and natural killer (NK) cells. Western blot analysis revealed that fractalkine protein was detected as a 95 kDa band in both the amniotic fluid and the amnion during the second and third trimesters. Immunohistochemistry using an anti-fractalkine polyclonal antibody revealed positive staining of epithelial cells in amnion and trophoblasts in both the second and third trimesters. Neonatal urine also contained detectable amounts of fractalkine. RT-PCR detected fractalkine mRNA transcripts in the amnion. To determine whether fractalkine receptor (CX(3)CR1)-positive cells were present in amniotic fluid and amnion, we performed RT-PCR using specific primers for CX(3)CR1. CX(3)CR1-positive cells had migrated into the amniotic fluid and the amnion. The present findings suggest that fractalkine found in amniotic fluid may contribute to the immunodefence mechanism during pregnancy.