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Development of Purified Cells In Vitro
The appearance of the A2B5(+) cells in purified long
term monolayer cultures made from day 12 and 13 cells
differed markedly from that of A2B5(+) cells from day 7 and
8 (Chapter 2). Instead of appearing to be neurons, the
majority of A2B5(+) cells exhibited a flattened glial and
then round morphology. They also expressed the glial
antigens GFAP and 5A11 in monolayer culture. These
combinations of antigen expression (A2B5 with 5A11 or GFAP)
were not found in unpurified cultures and are believed to
be abnormally induced by the purifications. Likewise, in
mouse cerebellar cultures other workers have experimentally
induced the expression of A2B5 antigen on the surfaces of
GFAP containing astrocytes as a result of neuronal
depletion by complement mediated lysis using an independent
neuronal marker (Nagata et al., 1986). Thus, the presence
of A2B5 antigen on vertebrate astrocytes which have been in
culture for even short periods of time (hours) should not
be considered characteristic of a normal phenotype without
reservation due to the apparent ease with which the antigen
can be modulated.
Another phenotype that was presumably artifactually
induced as a result of the purifications was flat cells
containing dense networks anti-neurofilament-M reactive
filaments. Some of these cells appeared to exhibit low
level surface A2B5 reactivity, but the majority appeared to