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for optimum separations of dissociated embryonic brain
cells. It was necessary to mix cells and microspheres in a
medium containing DNase. This was presumably due to the
release of DNA due to cell lysis. Various types of
separation chambers have been used for clinical
applications (Gee et al., 1987; Treleaven et al., 1984).
The chamber that was used for separation was much simpler
than those used for bone marrow purging. This open system
proved to be entirely satisfactory and contamination due
to this never occured. Lastly, satisfactory separations
were obtained with a much lower microsphere/target cell
ratio than is used for marrow purging. This is believed to
be due to increased collisions between target cells and
microspheres as a result of a higher percentage of target
cells (50%) than in infected bone marrow (=1%).
A2B5 Antigen and its Modulation
A2B5 (Eisenbarth et al., 1979) was chosen as the
target cell antibody for the immunomagnetic separations.
This was because of its high specificity for neurons in
long-term monolayer cultures of dissociated differentiated
tectum cells. Other factors that led to its choice were
that it has been reported to be neuron specific in humans
(Kim, 1985; Kim et al., 1986) and to bind to most or all
neurons in chick brain (Schnitzer and Schachner, 1982). The
antigen it recognizes is also a protease resistant
ganglioside (Eisenbarth et al., 1979; Kasai and Yu, 1983).