Abstract
Purpose :
Uncontrolled T cell activation can result pathological conditions including autoimmunity and graft rejections. Our group has previously shown that mesenchymal stem cells (MSCs) inhibit activation of innate immune cells including neutrophils and macrophages. Here, we investigate whether MSCs regulate T cell responses by secreting interleukin-11 (IL-11).
Methods :
Human bone-marrow derived MSCs (hMSCs) were purchased and phenotypically characterized for their expression of CD45- CD34- CD73+ CD90+. CD4+ CD25- T cells (purity: >95%) were magnetically sorted from human peripheral blood mononuclear cells for the MSC-T cell co-culture assays. Expression and secretion of IL-11 by hMSCs were evaluated using real-time PCR and ELISA, respectively. Expression of IL-11 receptor was confirmed in activated CD4+ CD25- T cells using flow cytometry. CD4+ CD25- T cells stimulated with anti-CD3/CD28 beads (1:1 ratio) were co-cultured with MSCs at 1:1 ratio for 24 hours (for early activation) and 66 hours (for proliferation) in the presence and absence of hIL-11 neutralizing antibody (20 µg/ml). Early T cell activation was assessed by evaluating expression of CD40L and CD69 (Median Fluorescence intensity; MFI) using flow cytometry. For proliferation, CD4+ CD25- T cells were stained with CFSE prior to co-culture and their proliferation was quantified by measuring CFSE dilution via flow cytometry.
Results :
hMSCs constitutively express high levels of IL-11 at both mRNA and protein levels. Naïve CD4+ CD25<font size="1">-</font> T cells showed the expression of IL-11 receptor, which was upregulated by 2-fold following CD3/CD28 stimulation. hMSCs significantly suppressed early activation of naive T cells, as indicated by an approximate 70% reduction in expression of both CD69 (p=0.025) and CD40L (p=0.011). This MSC mediated reduction in early T cell activation was not observed following the neutralization of IL-11. Furthermore, our CFSE dilution assay demonstrated that hMSCs significantly prevented the proliferation of CD4+ CD25<font size="1">-</font>T cells (p=0.006); however, this MSC-mediated suppression of proliferation was abrogated following IL-11 neutralization.
Conclusions :
IL-11 secretion by human mesenchymal stem cells is critical for inhibition of early T cell activation and proliferation.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.