Differing PD-1 expression identifies sub-populations with higher
significance
Additionally, we assessed whether PD-1 positive T cells expressed PD-1
at different levels according to the PD-1 MFI (Figure 6 A). We found
that PD-1 low T cells were not significantly increased between controls
and patients, while two other gates that we labeled intermediate
(PD-1int) or high level
(PD-1hi)
identified PD-1 positive populations that were significantly increased
in patients with cancer and precursor lesions (Figure 6 B, F).
We also investigated whether PD-1int (Figure 6 C-E)
and PD-1hi (Figure 6 G-I) T cells co-expressed TIGIT
and Tim-3. We saw a significant increase of the
PD-1intTim-3+ population in the CC
group in comparison with the HD group (Figure 6 D). Interestingly, we
also found a significantly higher percentage of
PD-1int and PD-1hiCD3+ cells co-expressing TIGIT. The percentages of
those triple positive (PD-1-TIGIT-Tim-3) PD-1int and
PD-1hi CD3+ cells were also
increased in cancer patients
(Figure 6 E,
F), which might suggest an
exhausted T cell phenotype. It was notable that the stratification of
the PD-1 positive T cells allowed visualization of more significantly
separated populations of cells with checkpoint markers between HD and
CC, and higher levels of significance. PD-1hi, and
both PD-1hi TIGIT+ and
PD-1hiTIGIT+Tim-3+cell populations were also significantly increased in LG, and LG and HG
respectively (Figure 6 F-I).