Differences in immune cell invasion into the cerebrospinal fluid and brain parenchyma during cerebral infusion of interleukin-1β

Abstract.

Cytokine-mediated inflammatory cell recruitment into the brain is a critical step in the response to diverse insults, including infection, trauma, and stroke. Hence, continous intra-cerebroventricular infusion of interleukin (IL)-1β leads to an impressive cell invasion into the cerebrospinal fluid, as well as the brain parenchyma. Neither tumor necrosis factor-α nor IL-6 induced any significant cell invasion at all. However, the diverse immune cells (granulocytes, monocytes/macrophages) showed a different time course of invasion. Moreover, there was an association between the number of infiltrating immune cells and the infused IL-1 concentration. By analyzing intra-brain immune events, we demonstrated a time- and dose-dependent induction of intercellular adhesion molecule (ICAM)-1, whereas there were no differences for P-selectin, vascular cell adhesion molecule (VCAM)-1, and monocyte-chemotractant protein (MCP)-1, comparing vehicle and IL-1-infused animals. In conclusion, we assume IL-1β to be a key cytokine for the granulocyte and monocyte recruitment into the central nervous system after various insults. However, granulocytes anticipate monocyte invasion.