VF;IL-1β−/− mice showed only slightly reduced red cell parameters, and overall no significant changes in platelet and leukocyte counts compared to VF. In contrast, transplantation of VF;IL-1β−/− bone marrow into WT recipients resulted in decreased platelet counts, reduced infiltration of megakaryocytes in BM and spleen and reduced degree of myelofibrosis and osteosclerosis (Fig. 4a–c). The gene discussed is IL1B; the disease is osteosclerosis.