Examining the Effect of Dexamethasone on Immune Cells

Although the immune system is a powerful tool for combating infections, excessive immune activation can elicit numerous long-term health complications calling for the need for medication with a potential target of modulating immunoregulatory cells. Dexamethasone is a corticosteroid with a wide range of applications and is known for its anti-inflammatory and immunosuppressive effects. Futhermore, previous research by the Elahi lab indicated that newborns are enriched with immature red blood cells (CD71+ Erythroid Cells (CECs)) that actively suppress newborn immune systems, reducing excessive immune activation which could otherwise aggravate immune development. In this study, we aimed to investigate the role of dexamethasone on immune cells using a murine model. BALB/c littermate mice up to a week old and mice over 10-weeks-old were used for the experiments. Treated mice were injected with dexamethasone and control mice with PBS. To examine the effect of dexamethasone in the spleen and bone marrow, cells were isolated and used for immunophenotyping and in various functional assays. In comparison to control mice, we found that mice injected with dexamethasone displayed lower levels of CECs and increased levels of matured red blood cells (RBCs) in the spleen. In contrast, the bone marrow displayed higher levels of CECs and decreased RBCs. Both trends were consistent in neonatal and adult mice. Intriguingly, we observed that treated mice also had increased numbers of Ly6G and Ly6C single or double-positive cells in the spleen and bone marrow of both neonatal and adult mice, with a higher effect observed in neonatal mice. In addition, isolation of these expanded cells and co-culture with responder T-cells showed an enhanced proliferation effect in vitro. Our findings present an investigation into the role of dexamethasone on immune cells, giving further insight into its numerous diverse impacts on various immunoregulatory cells.