PD-L1 expression
Monocyte PD-L1 expression, as measured by flow cytometry, is illustrated in Figure 3. Under control conditions, PD-L1 expression remained low throughout the 18 h duration. Interestingly, both the addition of either LPS or IFN-γ led to similar increases in monocyte PD-L1. Under both conditions, PD-L1 expression reached 76.05 (± 14.2) and 85.71 (± 15.7) MFI, respectively, both higher than control conditions at 18 h (p = 0.020 and p = 0.012, respectively).
The combination of LPS and IFN-γ led to an early synergistic increase in monocyte PD-L1 expression at 6 h, higher than with either alone (p = < 0.0001 for both comparisons). By 18 h, further increases in PD-L1 expression were observed reaching 203.39 (± 29.3) MFI, again, higher than either LPS or IFN-γ alone (p = < 0.001 for both comparisons).