CD4+CD25+FOXP3+ regulatory T cells are effective suppressors of the adaptive immune system. However, the nature of their interactions with innate immune cells, such as monocytes, is less well characterised. Previous data from our lab showed that Tregs can modulate monocyte function, including a down-regulation of LPS-induced IL-6 release that can persist for 48 hours after Tregs have been removed from co-culture, suggesting a long-lasting mechanism of modulation. The current work aims to further characterise and examine the molecular basis for Treg-mediated monocyte modulation.
Human CD14+ monocytes were isolated by MACS separation. CD4+CD25+CD127low regulatory T cells (Tregs) CD4+CD25-CD127high and effector T cells (Teffs) were purified using FACS sorting. CD14+ monocytes were cultured alone or at a 2:1 ratio with autologous Tregs or Teffs with anti-CD3 mAb for 16/40 hours, followed by LPS addition.
LPS-induced pro-inflammatory cytokine production was decreased in monocytes upon co-culture with Tregs and increased upon co-culture with Teffs, when measured by ELISA or MSD (TNFα, IL-6, IL-8, n=11) and intracellular staining (IL-6, TNFα, n=6). Monocytes co-cultured with Teffs displayed increased expression of CD80, CD86 and HLA-DR, whereas monocytes co-cultured with Tregs displayed increased expression of CD163, measured by flow cytometry (n=8). These results indicate that Tregs modulate monocyte function and phenotype. We are currently analysing the gene expression profiles of CD14+ monocytes following co-culture without/with Tregs vs. Teffs, using RNA-sequencing. Our aim is to identify differentially expressed genes of interest and characterise the molecular mechanisms underlying modulation of monocytes by Teffs/Tregs.
Supported by a BBSRC CASE studentship (BB/L014165/1)