Role of the endometrial tripod interleukin-18, -15, and -12 in inadequate uterine receptivity in patients with a history of repeated in vitro fertilization-embryo transfer failure.

OBJECTIVE: To document in the endometrium the correlation among the interleukin (IL)-12, -15, and -18 mRNA and the correlation between cytokine levels, vascular status, and endometrial natural killer (NK) cell count in the context of recurrent implantation failure.
DESIGN: A pilot study.
SETTING: Department of Reproductive Immunology. PATIENT(S): Women who failed to become pregnant after repeated IVF-embryo transfer and fertile control subjects. INTERVENTION(S): Ultrasonic evaluation and endometrial biopsy in luteal phase. MAIN OUTCOME MEASURE(S): Uterine artery Doppler, count of uterine CD56 bright cells/field, and quantification by real-time polymerase chain reaction (PCR) to monitor IL-12 family (IL-12p40, IL-12p35, EBI3, IL-23), the IL-18 system (IL-18, IL-18R, IL18BP), and the IL-15 mRNA ratio. RESULT(S): The uterine artery Doppler and the CD56 bright cell counts were significantly different in fertile and infertile patients. The mean uterine artery pulsatility index correlated significantly negatively with the IL-18/actin ratio suggesting a defect of the cytokine-dependent vascular remodeling pathway. The number of uterine CD56 bright cells was significantly correlated with the IL-15/actin and IL-18/IL-18BP ratios. Thus, IL-18 and IL-15 seems to be involved in the local recruitment and the activation of uterine natural killer (uNK) cells. IL-18 was itself correlated with IL-15 and IL-12, suggesting a local control of uNK cells activation. CONCLUSION(S): The assessment of the tripod IL-12/-15/-18 shows distinct immune-related mechanisms that are involved in the broader context of inadequate uterine receptivity.