RNA-seq of spleen monocytes from IL-4Ra+/+ and IL-4Ra-/- mice on a C57BL/6J background

Monocytes are immune cells which differentiate into subsets through sequential transition. The life-time differs between the individual subsets ranging from 1 day to 1 week. We studied the involvement of IL-4 receptor signaling on monocyte survival in mice lacking IL-4 receptors in a total knockout and a myeloid knockout. Circulating leukocytes were reduced by 25% in both knockouts, which was mainly caused by a 50% reduction of monocytes. Using RNA sequencing we were able to demonstrate that spleen monocytes in IL-4Ra deficient mice express lower amounts of anti-apoptotic genes and increased amounts of cell adhesion molecules hinting to an increase in apoptotic potential of these cells. This data were also verified in spleen samples were we found an increase of apoptotic monocytes identified by TUNEL and cleaved caspase 3 staining. Mechanistically we were able to show that IL-4 signaling directly affects the lifespan of monocytes in vivo. Therefore, we identified a previously unknown function of basal IL-4 levels in homeostasis of monocytes by regulating the lifespan and preventing apoptosis of the cells. Overall design: RNA-seq of spleen monocytes from 3 IL-4Ra+/+ and 3 IL-4Ra-/- mice, isolated from splenocytes by negative selection using a commercial antibody cocktail and magnetic beads