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When compared with immunostaining for neurofilaments of
freshly dissociated cells it was found that a small
percentage of NF(+) cells were A2B5(-). The majority of the
NF(+) cells, however, were A2B5(+) (83%) and were removed.
Thus the specificity of A2B5 for neurons initially is not
complete and all-inclusive but encompases the majority of
identifiable neurons. No other markers that react with
differentiated neurons are known that react with 7 or 8 day
cells. Neuron specific enolase in chick brain does not
appear until later in development and apparently is not
produced in brain cell cultures (Ledig et al., 1985). Aside
from markers, culturing cells on neuron-selective
polyornithine suggests that at least most of the A2B5(+)
cells were neurons because the microsphere fraction was
enriched for neurons and the purified A2B5(-) cultures did
not contain them.
The appearance of A2B5 antigen on the surfaces of the
purified A2B5(-) cells was curious. This phenomenon was
first observed when the purified cells were incubated in
A2B5 and then the fluorescent secondary antibody. This was
done for fear that some A2B5(+) cells may have quickly
cleared the monoclonal from their surfaces after the
separation. Subsequent experiments revealed that no
reduction in the number of A2B5(+) cells occured after a
day in culture (data not shown). Therefore, the correct
assay to assess the degree of depletion of A2B5(+) cells