INTERLEUKIN-1-BETA AND ITS TYPE-1 RECEPTOR ARE EXPRESSED IN DEVELOPING NEURAL CIRCUITS IN THE FROG, XENOPUS-LAEVIS

The cytokine interleukin-1 beta (IL-1 beta) is an evolutionarily conse rved molecule that was originally identified in the immune system. In addition to regulating peripheral immune responses, IL-1 beta plays an important role in mediating neural-immune interactions and regulating glial activities during healing and repair in the damaged nervous sys tem. Active IL-1 beta is produced by interleukin-converting enzyme (IC E), a caspase thought to be involved in the induction of apoptosis. We report that, in the developing frog, Xenopus laevis, IL-1 beta and th e IL-1 type 1 receptor proteins are coexpressed in specific neurons th at comprise early sensory-motor circuits. IL-1 beta and IL-1 type 1 re ceptor proteins are colocalized in specific midbrain and hindbrain ret icular cells, including Mauthner's neuron; specific cells in the trige minal (fifth), lateral line (seventh), and vestibular (eighth) cranial ganglia; oculomotor neurons; and the primordial Purkinje cells of the lateral cerebellar auricle, In the spinal cord, Rohon-Beard sensory n eurons, dorsal root ganglion cells, and primary motoneurons are immuno positive. Anteriorly, the olfactory pits, olfactory nerves, and olfact ory bulbs are labeled, as are retinal cells, especially photoreceptor inner segments. With regard to the function of IL-1 beta during neural development. IL-1 beta and its type 1 receptor are present throughout the course of neural development in identifiable, long-lived neurons, such as Mauthner's neuron. These and other data suggest that IL-1 bet a and its type 1 receptor may be involved in the maintenance of cell s urvival rather than induction of neuronal death. (C) 1998 Wiley-Liss, Inc.