Corticosteroids are anti-inflammatory, reducing the number and activity of various inflammatory cell types, including lowering blood lymphocyte, monocyte, and basophil counts and preventing neutrophils from reaching sites of inflammation. So why do corticosteroids increase the number of neutrophils in circulation? 

The effects of corticosteroids reducing the infiltration of neutrophils to sites of inflammation within tissues and increasing the number of neutrophils staying in circulation are two sides of the same mechanism.

Surface expression of proteins, such as L-selectin, is involved in the rolling capture and adherence of neutrophils to blood vessel walls, which is necessary to enable extravasation through blood vessel walls and migration into tissues. Corticosteroids acting via glucocorticoid receptors regulate the expression of many genes involved in inflammatory responses. Continue reading