6
complement. "Panning" (Wysocki and Sato, 1978) is an
immunoselection method that allows for recovery of both
cell types; however, the purity of cells obtained is
marginally acceptable (95%) for most applications.
One negative separation method that utilizes
monoclonal antibody binding to a target cell population to
remove it from a mixed population is immunomagnetic
purging. This method was developed for removing
neuroblastoma cells from human bone marrow (Treleaven et
al., 1984) and operates by attaching the target cells to
paramagnetic polystyrene microspheres via antibody linkages
and removing them with a magnet. Potentially all types of
monoclonal antibodies against cell surface constituents can
be used, and routine separations result in depletions of
target cells by 4 to 5 orders of magnitude (Philip et al.,
1987 ) .
I have modified this method to work well with
dissociated embryonic chick brain cells. In hopes of
purifying immature glia for in vitro reassociation studies,
I removed the majority of identifiable neurons by using
the monoclonal antibody A2B5 (anti-ganglioside Gqi=;
Eisenbarth et al., 1979). It was found that even though the
initial purification of A2B5(-) cells was complete, by 24
hours in culture approximately 50% of these cells had
become A2B5(+). This modulation of cell surface A2B5
antigen was found to be in direct response to the