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This review introduces the field of cytokines and implantation and then recalls the specialized role of the uterus and the notion of the 'implantation window'. The role of inflammatory and angiogenic cytokines is presented, as well as the involvement of cytokines such as -interferons in corpus luteum maintenance in non-chorionic gonadotrophin-producing species. -Interferons are reviewed, before dealing with the more in depth analysis of cytokine networks in the pre- and peri-implantation uterus. The emerging involvement of cytokines in controlling uterine vascularization angiogenesis is reviewed, with emphasis on NK activating factors.

This review introduces the field of cytokines and implantation and then recalls the specialized role of the uterus and the notion of the ‘implantation window’. The role of inflammatory and angiogenic cytokines is presented, as well as the involvement of cytokines such as -interferons in corpus luteum maintenance in non-chorionic gonadotrophin-producing species. -Interferons are reviewed, before dealing with the more in depth analysis of cytokine networks in the pre- and peri-implantation uterus. The emerging involvement of cytokines in controlling uterine vascularization angiogenesis is reviewed, with emphasis on NK activating factors.

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.