Weber M, et al. - Researchers evaluated if there is an association between changes of PD-L1 and PD-L2 expression in blood and survival in oral squamous cell carcinoma (OSCC) and if such alterations could be an immune monitoring parameter. They also investigated whether tissue and blood samples of OSCC patients vs healthy controls had differentially expressed PD-L2. The link between PD-L2 expression and histomorphologic and prognostic tumor parameters was also determined. Findings were suggestive of the potential value of peripheral blood PD-L1 expression as a prognostic marker for OSCC patients. Also, peripheral blood PD-L1 expression could possibly serve as a parameter to monitor immune dysfunction in malign diseases. A possible greater relevance of PD-L1 for immune tolerance vs PD-L2 was noted in the peripheral blood. The possible potential utility of local PD-L2 expression in tissue samples was suggested as a diagnostic parameter for malignancy and as a contributor to the immunosuppressive local microenvironment in OSCC.