Characterization of the recently described CD8+HLA-DR+ regulatory T cells within the liver

MACHICOTE, A. ; PODHORZER, A. ; BILLORDO, A. ; BAZ, P. ; MONTAL, S; ARRUVITO, L. ; BELEN, S; PODESTA, G. ; FAINBOIM, L.

Capital Federal

Congreso; SAIC/FAIC 2015; 2015

Sociedad Argentina de Inmunología

Background. We have shown that CD8+ T cells from both adult peripheral blood and umbilical cord blood mononuclear cells constitutively expressing HLA-DR represent a natural human CD8+ regulatory T cell subset (CD8+DR+Tregs), acting through cell contact and involving CTLA-4. Our aim is to characterize CD8+ Tregs subset within the liver tolerogenic microenvironment.Methods. T cells markers were analyzed by flow cytometry on MNC of PB healthy controls (N=32) or from donor liver perfusion collection (N=10). Depletion of CD8+DR+ from liver MNCs was achieved by cell sorting with a FACSAria II flow cytometer. Detection of FOXP3 with anti-FOXP3 antibody was performed using fixed and permeabilized cells following the manufacturer?s instructions.Results. Within the liver (n=14), CD8+ T cells represent 63±11.9% and CD4 T cells 18±6.2% of CD3+ cells. Of note, CD4+FOXP3+ were only detected in 2±1.2% of liver CD4+ T cells. In contrast, CD8+HLA-DR+ T cells account for 44.7±16.4% of total CD8+ cells (n=14) vs. 14.4±3.5% in PB (n=32). After PMA stimulation, liver CD8+HLA-DR+ express high levels of IFN-γ and CD107a. Depletion of CD8+HLA-DR+ T cells enhances MNCs proliferative response to PHA, which was abrogated by restitution of CD8+HLA-DR+ cells.Conclusions. IDO, a known target of IFN-γ, is present in liver stellate cells, DC, kupffer cells, or T cells subsets. It remain to be elucidated if the high frequency of liver CD8+HLA-DR+ could mediate through IDO their immunosuppressor effect and contribute to the tolerogenic capacity of the liver.