23
had become A2B5(+) (Fig.2-3). This is the same level of
A2B5(+) cells in unpurified cultures after one day in
vitro. Plating efficiencies of both unpurified and purified
cells after one day in culture were nearly identical and
ranged from approximately 85-100% as determined by
retrospective counts from slides. Unpurified monolayer
cultures (1-2 weeks in vitro) contained A2B5(+) cells that
exhibited only neuronal morphologies that rested atop a
layer of A2B5(-) flat cells either singly or in
multicellular aggregates (Fig.2-4). Similarly, A2B5(+)
cells with neuronal morphologies with a layer of A2B5(-)
flat cells beneath them were present in monolayers from
purified cells. The clusters of A2B5(+) neurons in both
types of cultures appeared to be the same visual density
under high or low magnification. No difference in the
amount of A2B5(+) neurons in either type of culture was
seen. The cultures made from microsphere cells, however,
always contained visually larger and/or more numerous
aggregates of A2B5(+) neurons than did the unpurified or
purified cultures (not shown).
To assess the requirement of serum (FBS) in purified
cultures where A2B5 antigen was modulated, purified cells
were plated on polyornithine coated coverslips as above.
After one day in culture, cells were immunostained live
with A2B5 as above. To determine whether or not the
modulated A2B5 antigen was trypsin-resistant as was the