TLR4 and primary myelofibrosis: To assess the contribution of TLR4 and TLR2 to cytokine production from monocytes, we studied baseline and TLR-stimulated gene expression of two inflammatory cytokines, IL-1β, which in addition to mediating vascular inflammation and bone marrow fibrosis, has been reported to promote clonal expansion of hematopoietic progenitors in MF (39, 40) and IL-6, a prototypic inflammatory cytokine.