Phenotyping of BM TpMos and Mature Ly6Chi monocytes in steady state and during sepsis

Circulating monocytes are crucial for tissue resident macrophage (TRM) replenishment. While a temporary loss of TRMs does not impose immediate danger to the host in sterile conditions, the niche comprising of dying macrophages in the presence of pathogenic bacteria predisposes the host to increased morbidity if these cells are not effectively replaced. Importantly, monocytes have been shown to be susceptible to cell death after executing effector functions such as phagocytosis. Hence, the demands and contribution of monocytes in pathogen clearance and macrophage differentiation is perplexing. Interestingly, we show that proliferating transitional pre-monocytes (TpMos), an immediate precursor of mature Ly6Chi monocytes (MatMos), were mobilized into the periphery in response to acute bacterial infection and sepsis. Since TpMos are absent in the circulation in the steady state, we aim to understand how TpMo recruitment into the periphery may result in differing functions from MatMos during sepsis. Mice were subjected to cecal ligation and punture (CLP) to induce sepsis. Age- and gender-matched sham-operated mice were included as control. BM TpMos and mature Ly6Chi monocytes were sorted 6 days post-surgery for RNA isolation.