Monocytes are able to differentiate to dendritic cells (DCs) under inflammatory situations. Different monocyte subsets show distinct inflammatory cytokine profiles and differentiation potential under steady-state and inflammatory situations. The major subset of monocytes consists of CD14-high CD16-negative (CD14++CD16−). Commited dendritic cell originated from immature monocytes. In humans (hpre-CDC) that develops from committed DC progenitors (hCDPs) in the BM.

We have measured the number of immature monocytes (pre-CDC) with CD34+CD38+ CD116+ expression by flow cytometry with acquisition of a million cells from peripheral blood in 20 newborn and 20 adults. To determine the physiological distribution of hpre-CDCs in adult humans, we examined, peripheral blood, of newborn and adult for small numbers of pre-CDCs travel through the blood and replace cDCs in the peripheral organs, maintaining homeostasis of the highly dynamic cDC pool.

Monocyte-derived circulating short-lived pre-CDCs are high in newborn than adults. We assume that any organ includes epithelial cells, endothelial cells, fibroblasts, stromal cells, and hematopoietic cells are a source of GM-CSF secretion. Circulations of CD116+ short-lived pre-CDCs undergo maturation when going through the vascular environment with high GM-CSF secretion.