Using the Spleen as an In Vivo Systemic Immune Barometer Alongside Osteosarcoma Disease Progression and Immunotherapy with α-PD-L1

Table 7

Treatment with α-PD-L1 significantly reduces TCES but does not affect parent populations of LLCs in the spleens of TF tumor-bearing mice.

Population	TF (−) α-PD-L1 % expression/TCES	TF (+) α-PD-L1 % expression/TCES	p
CTLs	2.73 ± 1.22%	2.85 ± 1.13%	0.9
Ths	6.45 ± 3.08%	5.14 ± 3.74%	0.61
Tregs	21.09 ± 5.12%	26.63 ± 7.02%	0.24
CTLA-4^+ CTLs	18.35 ± 10.12%	44.95 ± 37.19%	0.16
TCES	18.23 ± 4.58	0.79 ± 0.71	0.00072

Spleens were harvested at approximately 11 weeks post-inoculation and the tissue was subjected to Panel 3 (mod) for immune cell population analysis from n = 5 (−) α-PD-L1 and n = 3 (+) α-PD-L1 TF tumor-bearing mice. For treated mice, 20 μg of α-PD-L1 was given in PBS via intraperitoneal injection twice a week starting when tumors were first palpable. The statistics for each group are summarized accordingly with significance being assigned to those populations presenting values < 0.01 from a two-tailed Student’s T-test with Bonferroni correction and 95% confidence as denoted by an asterisk. PD-L1 = programmed death-ligand 1; TF = transfected; LLC: lymphoid lineage cell; CTL = cytotoxic T lymphocyte; Th = T helper cell; Treg = T regulatory cell; CTLA-4⁺ CTL = cytotoxic T-lymphocyte-associated protein 4 positive cytotoxic T lymphocyte; TCES = T-cell exhaustion status.