Lymphocyte HLA-DR/CD-38 co-expression correlates with Hodgkin lymphoma cell cytotoxicity in vitro independent of PD-1/PD1-L pathway

The interactions between Hodgkin and Reed Sternberg cells and tumor microenvironment, the changes that occur with therapy and, in particular, checkpoint inhibition are not fully understood. Understanding these is key to optimizing outcomes for patients with Hodgkin lymphoma (HL). We evaluated the immunophenotypic characteristics of cytotoxic, helper T and NK lymphocytes upon in vitro stimulation, cell-mediated cytotoxicity against HL cells, HDLM-2 and KM-H2, and the association with effector cell activation state, as well as changes in cytotoxicity following PD-1 or PDL-1 blockade. Higher HLA-DR/CD38 expression on effector cells was associated with increased cytotoxicity against HL cells. All effector cell types were cytotoxic of HL cells, though achieved maximum activation and cytotoxicity at variable timepoints. HLA-DR/CD38 co-expression correlated with cytotoxicity, but PD-1 expression did not. There was no significant change in cell-mediated cytotoxicity following PD-1/PDL-1 blockade. The mechanism of action of checkpoint inhibitors may not be limited to direct PD-1/PDL-1 blockade.