CD34 and myelodysplastic syndrome: Furthermore, they reported that impaired clearance of apoptotic cells by macrophages in the bone marrow of patients with MDS is associated with increased circulating levels of the endogenous TLR agonist high mobility group protein B1 (HMGB1), and they concluded that this contributes to enhanced proinflammatory cytokine production by monocytes and impaired clonogenic potential of CD34+ cells in MDS patients.