Innate lymphoid cells at the human maternal-fetal interface in spontaneous preterm labor

Abstract

Problem: Pathological inflammation is causally linked to preterm labor and birth, the leading cause of neonatal morbidity and mortality worldwide. Our aims were to investigate whether (i) the newly described family of innate lymphoid cells (ILCs) was present at the human maternal-fetal interface and (ii) ILC inflammatory subsets were associated with the pathological process of preterm labor.

Methods of study: Decidual leukocytes were isolated from women with preterm or term labor as well as from gestational age-matched non-labor controls. ILCs (CD15^- CD14^- CD3^- CD19^- CD56^- CD11b^- CD127⁺ cells) and their subsets (ILC1, T-bet+ ILCs; ILC2, GATA3+ ILCs; and ILC3, RORγt+ ILCs) and cytokine expression were identified in the decidual tissues using immunophenotyping.

Results: (i) The proportion of total ILCs was increased in the decidua parietalis of women with preterm labor; (ii) ILC1s were a minor subset of decidual ILCs during preterm and term gestations; (iii) ILC2s were the most abundant ILC subset in the decidua during preterm and term gestations; (iv) the proportion of ILC2s was increased in the decidua basalis of women with preterm labor; (v) the proportion of ILC3s was increased in the decidua parietalis of women with preterm labor; and (vi) during preterm labor, ILC3s had higher expression of IL-22, IL-17A, IL-13, and IFN-γ compared to ILC2s in the decidua.

Conclusion: ILC2s were the most abundant ILC subset at the human maternal-fetal interface during preterm and term gestations. Yet, during preterm labor, an increase in ILC2s and ILC3s was observed in the decidua basalis and decidua parietalis, respectively. These findings provide evidence demonstrating a role for ILCs at the maternal-fetal interface during the pathological process of preterm labor.

Keywords: cytokine; decidua; inflammation; innate immunity; interleukin; mucosal immunity; parturition; pregnancy; tolerance.

Figure 1

ILCs are present at the human maternal-fetal interface. (A) Mononuclear cells were isolated from the decidua parietalis and decidua basalis. Flow cytometry gating strategy for immunophenotyping of ILCs. ILCs (CD127+) were initially gated within the viability gate and linage negative (Lin−; CD15−CD14−CD3−CD19−CD56−CD11b−) gate. Red boxes represent the lineage negative populations. Representative flow cytometry contour plots show the expression of CD127 by ILCs from the decidua parietalis and decidua basalis. The proportion of total ILCs in the decidua parietalis (B) and decidua basalis (C) of women who underwent spontaneous preterm (PTL) or term (TIL) labor and those who delivered preterm (PTNL) or term (TNL) without labor. n=8–25 per group.

Figure 2

ILC1s are a minor population in the decidua. (A) Mononuclear cells were isolated from the decidua parietalis and decidua basalis. Flow cytometry gating strategy for immunophenotyping of ILC1s. ILCs (CD127+) were initially gated within the viability gate and linage negative (Lin−; CD15−CD14−CD3−CD19−CD56−CD11b−) gate. Representative flow cytometry contour plots show the expression of T-bet by ILC1s from the decidua parietalis and decidua basalis (red dots). Isotype controls are shown as black dots. The proportion of ILC1s in the decidua parietalis (B) and decidua basalis (C) of women who underwent spontaneous preterm (PTL) or term (TIL) labor and those who delivered preterm (PTNL) or term (TNL) without labor. n=8–25 per group.

Figure 3

ILC2s are the most abundant ILC subset in the decidua. (A) Mononuclear cells were isolated from the decidua parietalis and decidua basalis. Flow cytometry gating strategy for immunophenotyping of ILC2s. ILCs (CD127+) were initially gated within the viability gate and the linage negative (Lin−; CD15−CD14−CD3−CD19−CD56−CD11b−) gate. Red boxes represent the lineage negative populations. Representative flow cytometry contour plots show the expression of GATA3 by ILC2s from the decidua parietalis and decidua basalis (red dots). Isotype controls are shown as black dots. The proportion of ILC2s in the decidua parietalis (B) and decidua basalis (C) of women who underwent spontaneous preterm (PTL) or term (TIL) labor and those who delivered preterm (PTNL) or term (TNL) without labor. n=11–39 per group.

Figure 4

ILC3s are increased in the decidua parietalis of women who underwent spontaneous preterm labor. (A) Mononuclear cells were isolated from the decidua parietalis and decidua basalis. Flow cytometry gating strategy for immunophenotyping of ILC3s. ILCs (CD127+) were initially gated within the viability gate and linage negative (Lin−; CD15−CD14−CD3−CD19−CD56−CD11b−) gate. Representative flow cytometry contour plots show the expression of RORγt by ILC3s from the decidua parietalis and decidua basalis (red dots). Isotype controls are shown as black dots. The proportion of ILC3s in the decidua parietalis (B) and decidua basalis (C) of women who underwent spontaneous preterm (PTL) or term (TIL) labor and those who delivered preterm (PTNL) or term (TNL) without labor. n=11–39 per group.

Figure 5

Decidual ILC3s express IL-13 and IL-22 in women who underwent spontaneous preterm labor. (A) Mononuclear cells were isolated from the decidua parietalis and decidua basalis. Representative flow cytometry histograms show the mean fluorescence intensity (MFI) expression of IFNγ (red histograms), IL-13 (green histograms), IL-17A (orange histograms), and IL-22 (blue histograms) by decidual ILC2s and ILC3s (red dots). Isotype controls are shown as black outline histograms or as black dots. The MFI of IFNγ (B&F), IL-13 (C&G), IL-17A (D&H), and IL-22 (E&I) expression by ILC2s and ILC3s in the decidua parietalis (upper row) and the decidua basalis (bottom row) of women who underwent spontaneous preterm labor. n=23.