Interleukin-1-like activity in rat brain: sources, targets, and effect of injury.

Extracts of injured rat brain contained molecules that shared biological and physiochemical properties with interleukin-1 (IL-1). Brain IL-1-like activity increased following brain injury in parallel with the increase in astrocyte and fibroblast mitogenic activity. After 3 days postlesion, it reached about 20 times the basal (noninjured) level. Monoclonal antibodies to human IL-1 inhibited this brain IL-1-like activity. One of the cellular sources of brain IL-1-like activity seems to be astroglial cells. Primary cultures of purified rat brain astrocytes secreted into the culture medium more IL-1 activity than comparable numbers of peripheral blood monocytes. Brain IL-1, as well as authentic monocyte IL-1, appear to act on brain glial cells, promoting thymidine incorporation into purified astrocytes in culture.