To examine the direct effects of IL-4 on peripheral nervous system (PNS) we injected recombinant rat IL-4 (rrIL-4) into the sciatic nerve of normal adult Lewis rats. Histopathological and immunohistochemical observations revealed that 1 day after injection, a large number of macrophages and MHC class II-positive cells appeared within both the perineurium and endoneurium. Only few CD4(+)and CD8(+)T cells existed in the endoneurium. From day 4 to day 7, we observed a gradual decline of inflammation, but the number of infiltrates in rrIL-4 injected nerves was significantly higher compared with sterile PBS-injected control group. On the contrary, demyelination affected significantly fewer nerve fibres in the rrIL-4-injected nerves compared with control group on day 7. Intraneural injection of rrIL-4 results in high grade inflammation and mild demyelination in the PNS.
Copyright 2000 Academic Press.