Treg proliferation in HNC patients is not inhibited through PD1/ PDL1 interaction

Background Immunoregulatory mechanisms in the tumor microenvironment influence tumor progression and therapeutic response for both conventional therapies as well as immunomodulatory strategies. Regulatory T cells represent a key component for these mechanisms. Here, we investigate the influence of PD1/PD-L1 signaling on regulatory T cells of HNSCC patients. Experimental setting: Blood samples of HNC patients were collected. Isolation of CD4+ T cells was performed through negative selection with an enrichment kit. Cells were labeled with the proliferation marker CFSE. After stimulation with CD3/CD28 beads (control) or CD3/CD28/PDL1 beads over 5 days, cells were stained for CD3 (APC-Cy7), CD4 (PE-TR), CD25 (PE-Cy7), CD39 (APC), PD1 (PerCP-Cy5.5) and Tim3 (Brilliant Violet 421). A comparison of proliferation rates and surface markers was performed through flow cytometry