The observations that megakaryocytes represent an important source of IL-6 [24], support MOPC315.BM myeloma cells in co-culture, and are co-localized with MOPC315.BM myeloma cells in vivo, suggest that megakaryocytes can substitute for the supportive effect of eosinophils on myeloma growth in the bone marrow. This evidence concerns the gene IL6 and plasma cell myeloma.