Redistribution and internalization of antibodies to galactocerebroside by oligodendroglia

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Abstract
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.