TNFα is expressed in activated microglia/macrophages in the regions where many apoptotic OLs are recognized with severe demyelination. A: Double labeling of TNFα and RCA-1 of the twi/twi cerebrum at PND 40. Arrows indicate microglia/macrophages, which are double positive for TNFα and RCA-1. B-J : In twi/twi at PND 40, there are many TNFα-positive cells (B, E) as well as many TUNEL-positive cells (C, F) in the CWM and sp5, where severe demyelination was present as judged from the results of MBP immunostaining (D, G). These apoptotic cells are immunostained with pi-GST, identified to be OLs (inset in C). In the corpus callosum (cc), there are only a few TNFα-positive cells (H) and TUNEL-positive cells (I), where demyelination was milder than in the cerebellum (J). Asterisks and double asterisks represent the same region in the serial sections. Scale bars = 50 μm (B-J), 10 μm (inset in "C").