CD84 and B-cell chronic lymphocytic leukemia: Biochemical and structural studies indicate that CD84 forms homophilic dimers by self-association (18) and in doing so, enhances IFN-γ secretion (19) and induces programmed cell death ligand 1 (PD-L1) upregulation on chronic lymphocytic leukemia (CLL) cells, resulting in suppression of T cell activation against cancer cells (20).