CD19 and plasma cell myeloma: For myeloma cells, bone marrow cells were stained with anti CD45, CD19, CD38 and CD138, as well as PDL1 (CD274), or PDL2 (CD273), as described in Material and Methods and in supplementary information (Fig A in S2 File) PCs were identified as CD19-, CD38high cells since staining with anti-CD45 and CD138 varied (data not shown).