CCR2 and thrombotic thrombocytopenic purpura: With age-related TTP decline, as modeled in TTP global and myeloid-specific null mice, we showed a concomitant expansion of M-MDSCs and transcriptomic changes in the CCR2-CCL2 axis within bone marrow myeloid progenitor populations that may contribute to their mobilization from bone marrow and peripheral expansion.