PDCD1 and oral cavity squamous cell carcinoma: This observational, in vitro, cell culture-based study aimed to assess the concentrations of PD-1 and PD-L1 in the peripheral blood mononuclear cells (PBMCs) of patients with oral squamous cell carcinoma (OSCC) and compare their levels with those in healthy controls, both pre- and post-curcumin intervention.