Fig. 4: IL-21R-STAT3 axis promotes initial differentiation of trNK.

a Flow cytometry and the corresponding statistics showing compositional change of uterine NK in virgin mice and pregnant mice at the indicated gestational days (n = 3, 4, 4, and 3 per group). b Schematics of prediction for potential transcription regulators (related to Supplementary Fig. 4a). c Scatter plots showing the motif enrichment and expression of potential trNK-specific transcription regulators. d Dot plot showing the expression of cytokine receptors associated with STAT3 activation. e Flow cytometric histogram showing IL-21R expression on uterine trNK-V, trNK-D, trNK-T subgroups and cNK from gd8.5 mice (n = 4 per group; *P = 0.0152, *P = 0.0483, **P = 0.0011). f Quantitative PCR assessing Il21 expression in uteri at the indicated gestational days (n = 5, 5, 3, 3, and 3 per group; *P = 0.0258, *P = 0.0377). g Flow cytometric and statistical analysis of STAT3 phosphorylation in uterine trNK. Uterine trNK are sorted from virgin and gd6.5 mice, and stimulated in presence or absence of recombinant IL-21 for 30 min (n = 4 per group; *P = 0.0348, *P = 0.0316). (h-k) Uterine trNK-V subgroup is sorted from gd6.5 mice, and cultured in presence or absence of IL-21 and STAT3 inhibitor (iSTAT3) for 72 h. h Flow cytometric and statistical analysis showing the percentage of 4-1BB^-CD55^-, 4-1BB⁺CD55^-, 4-1BB^-CD55⁺ and 4-1BB⁺CD55⁺ trNK subgroups (n = 4 per group; ***P = 0.0010, **P = 0.0019, **P = 0.0011, **P = 0.0021, **P = 0.0078, *P = 0.0122). i Dot plot depicting the gene expression changes of in vitro cultured uterine trNK (h). j Heatmap showing expression change of the STAT3-dependent and -independent genes (i) k Scoring of the STAT3-dependent IL-21-upregulated genes in gd8.5 uterine trNK. Numbers indicate the percentages in each box. Data are shown as the mean ± SEM. P-values are calculated by two-sided unpaired t-test, *P < 0.05, **P < 0.01, ***P < 0.001. Data are representative of two independent experiments (b–d, i–k) or at least three independent experiments (a, e–h). Source data are provided as a Source Data file.