IGHG1 and hematopoietic and lymphoid system neoplasm: As MM is a type of blood cancer defined by the existence of unusual plasma cells in the boneEI marrow, we examined the average expression level of five genes (IGKC, IGHG3, IGHG4, IGHG1, IGLL5) in the six cell types and illustrated their expression patterns in Figure 1G.