High inflammation and mild demyelination in the peripheral nervous system induced by an intraneural injection of rr interleukin-4

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 ad ult Lewis rats. Histopathological and immunohistochemical observations reve aled that 1 day after injection, a large number of macrophages and MHC clas s II-positive cells appeared within both the perineurium and endoneurium, O nly 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 inf iltrates in rrIL-4 injected nerves was significantly higher compared with s terile PBS-injected control group. On the contrary, demyelination affected significantly fewer nerve fibres in the rrIL-4-injected nerves compared wit h control group on day 7. Intraneural injection of rrIL-4 results in high g rade inflammation and mild demyelination in the PNS. (C) 2000 Academic Pres s.