Murine trophoblast cells induce NK cell interferon-gamma production through KLRK1.

Murine models suggest that natural killer (NK) cells are important for normal implantation site development, in part, through the production of interferon gamma (IFNG). As KLRK1 (NKG2D) is expressed on human and murine uterine NK (uNK) cells, we examined the role of KLRK1 in the interaction between murine trophoblasts and NK cells. Flow cytometric analysis revealed that both murine trophoblast stem (TS) cells and differentiated trophoblast giant cells expressed the KLRK1 ligand retinoic acid early transcript 1, or RAET1. Coculture of activated NK cells with either TS cells or giant cells led to the production of IFNG, as measured by ELISA. In addition, coculture with TS cells led to the downregulation of KLRK1. Both responses were inhibited by soluble KLRK1 ligand, but not by irrelevant protein. Further studies demonstrated the presence of KLRK1 ligand on uterine cells derived from either virgin or pregnant mice, although uterine RAET1 protein expression was upregulated in vitro by progesterone, but not estradiol. We suggest that the interaction of KLRK1 and RAET1 may be involved in IFNG production by uNK cells, and thus, this receptor-ligand pair may contribute to successful murine implantation site development.

Anti-inflammatory activity and neutrophil reductions mediated by the JAK1/JAK3 inhibitor, CP-690,550, in rat adjuvant-induced arthritis.

BACKGROUND: The Janus kinase (JAK) family of tyrosine kinases includes JAK1, JAK2, JAK3 and TYK2, and is required for signaling through Type I and Type II cytokine receptors. CP-690,550 is a potent and selective JAK inhibitor currently in clinical trials for rheumatoid arthritis (RA) and other autoimmune disease indications. In RA trials, dose-dependent decreases in neutrophil counts (PBNC) were observed with CP-690,550 treatment. These studies were undertaken to better understand the relationship between JAK selectivity and PBNC decreases observed with CP-690,550 treatment. METHODS: Potency and selectivity of CP-690,550 for mouse, rat and human JAKs was evaluated in a panel of in vitro assays. The effect of CP-690,550 on granulopoiesis from progenitor cells was also assessed in vitro using colony forming assays. In vivo the potency of orally administered CP-690,550 on arthritis (paw edema), plasma cytokines, PBNC and bone marrow differentials were evaluated in the rat adjuvant-induced arthritis (AIA) model. RESULTS: CP-690,550 potently inhibited signaling through JAK1 and JAK3 with 5-100 fold selectivity over JAK2 in cellular assays, despite inhibiting all four JAK isoforms with nM potency in in vitro enzyme assays. Dose-dependent inhibition of paw edema was observed in vivo with CP-690,550 treatment. Plasma cytokines (IL-6 and IL-17), PBNC, and bone marrow myeloid progenitor cells were elevated in the context of AIA disease. At efficacious exposures, CP-690,550 returned all of these parameters to pre-disease levels. The plasma concentration of CP-690,550 at efficacious doses was above the in vitro whole blood IC50 of JAK1 and JAK3 inhibition, but not that of JAK2. CONCLUSION: Results from this investigation suggest that CP-690,550 is a potent inhibitor of JAK1 and JAK3 with potentially reduced cellular potency for JAK2. In rat AIA, as in the case of human RA, PBNC were decreased at efficacious exposures of CP-690,550. Inflammatory end points were similarly reduced, as judged by attenuation of paw edema and cytokines IL-6 and IL-17. Plasma concentration at these exposures was consistent with inhibition of JAK1 and JAK3 but not JAK2. Decreases in PBNC following CP-690,550 treatment may thus be related to attenuation of inflammation and are likely not due to suppression of granulopoiesis through JAK2 inhibition.