Redistribution and internalization of antibodies to galactocerebroside by oligodendroglia

Glial cultures from mouse brain were used to examine the direct interaction between oligodendroglia and antibodies to galactocerebroside (GalC). The external surface of oligodendroglial membrane sheets showed large GalC+ patches separated by a GalC- network after exposure to anti-GalC and fluoresceinated second antibody at 37 degrees C. However, the membrane sheets were evenly stained when cultures were fixed prior to staining or stained at 0 degrees C. Further, exposure to second antibody at 0 degrees C or to Fab fragments of second antibody at 37 degrees C also gave even staining. These results indicate that GalC is normally distributed evenly on the surface of oligodendroglial membrane sheets, but that redistribution or patching of GalC:anti-GalC complexes occurs by cross-linking with second antibody at 37 degrees C. Antibodies to GalC are internalized rapidly and specifically by oligodendroglia. This process is temperature-dependent, and, in contrast to patching, does not require the presence of second antibody. Internalized antibodies are seen within 1 min throughout oligodendroglial membrane sheets, then aggregate in the sheets and in large vein-like structures leading to the cell body. By 1 hr, the cell body is densely packed with vesicles containing anti-GalC. By 24 hr after a 10 min exposure to anti-GalC, internal antibody has disappeared. Anti-GalC is recycled to the cell surface within 5 min after exposure, and continues to appear on the surface for at least 4 hr after the pulse.