Primary unexplained infertility is associated with reduced expression of the T-regulatory cell transcription factor Foxp3 in endometrial tissue

Mol Hum Reprod. 2006 May;12(5):301-8. doi: 10.1093/molehr/gal032. Epub 2006 Mar 30.


A receptive endometrial environment requires adequate immunological tolerance to protect the implanting embryo from maternal immune rejection. Studies in mice implicate CD4+CD25+ T-regulatory (Treg) cells as essential mediators of immune tolerance in pregnancy. The aim of this study was to evaluate the link between Treg cells and fertility in women. Expression of Foxp3, a master regulator of Treg cell differentiation, was quantified in endometrial tissue from women experiencing primary unexplained infertility and normal fertile women. Endometrial biopsies were collected during the mid-secretory phase of the menstrual cycle from women meeting rigorously defined criteria for unexplained infertility after experiencing repeated failed cycles of IVF treatment (infertile, n = 10), or women classified as proven fertile (control, n = 12). Expression of Foxp3 mRNA was reduced approximately two-fold in the tissue of infertile women. In contrast, mRNAs encoding T cell transcription factors T-bet and GATA3, associated with differentiation of Th1 and Th2 CD4+ T cells respectively, were unchanged. Treg cell differentiation is controlled by TGFbeta, but the relative abundance in endometrial tissue of TGFbeta1, TGFbeta2, TGFbeta3 mRNAs was not changed in infertile women. Cytokines influencing Th1 and Th2 cell differentiation, including IFNgamma, IL-2, IL-4, IL-5, IL-10 and IL-12p40, as well as dendritic cell-regulating cytokines IL-1alpha, IL-1beta, IL-6, LIF, GM-CSF and TNFalpha were also expressed similarly regardless of fertility status. The finding of reduced endometrial Foxp3 implicates impaired differentiation of uterine T cells into the Treg phenotype as a key determinant of fertility in women. The factors underpinning this aberration in the immune response remain to be identified.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • CD4-Positive T-Lymphocytes / metabolism
  • Cytokines / genetics
  • Endometrium / metabolism*
  • Endometrium / pathology
  • Female
  • Forkhead Transcription Factors / genetics*
  • GATA3 Transcription Factor / genetics
  • Gene Expression
  • Humans
  • Infertility, Female / genetics*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • T-Box Domain Proteins
  • Th1 Cells / metabolism
  • Th2 Cells / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transforming Growth Factor beta / genetics


  • Cytokines
  • FOXP3 protein, human
  • Forkhead Transcription Factors
  • GATA3 Transcription Factor
  • GATA3 protein, human
  • RNA, Messenger
  • T-Box Domain Proteins
  • T-box transcription factor TBX21
  • Transcription Factors
  • Transforming Growth Factor beta