Immunohistochemical localization of interleukin-2 and its receptor subunits α, β and γ in the main olfactory bulb of the rat

Endogenous interleukin-2 (IL-2) was found in the adult rat brain, however, it has not been reported whether this cytokine is present in the olfactory bulb. Immunohistochemical techniques were used to examine the cellular localization of IL-2 and its receptor subunits in the main olfactory bulb of the rat. Strong IL-2 immunoreactivity was localized in glial cells, specifically in the olfactory nerve layer, glomerular layer and external plexiform layer. IL-2 mRNA was detected in the olfactory bulb by RT-PCR. All three IL-2 receptor subunits also showed distinct laminar distributions. The IL-2R alpha and IL-2R beta immunoreactivity was found both in neurons and glial cells, whereas IL-2R gamma imunoreactivity was found in glial cells, and thus resembled IL-2 immunostaining. The present results demonstrated a wide distribution of IL-2 and its receptor subunits in the main olfactory bulb of the rat, suggesting that IL-2 might play a role in the olfactory function through autocrine or paracrine pathways. The exclusive high expression of IL-2 in glial cells in distinct laminar structures, where neuron-glia interactions are closely associated with olfactory nerve regeneration, imply that IL-2 might be involved in the process of nerve regeneration in the olfactory bulb. (C) 2001 Elsevier Science B.V. All rights reserved.