Expression of GFAP (glial fibrillary acidic protein) antigenicity and differentiation of glioma tumor cells of astrocytic origin

Polyclonal antibodies were used in the diagnostic procedure of brain tumors of astrocytic origin. Investigations were undertaken to determine the percentage of GFAP positive and negative cells in arbitrary selected fields of the tumor specimen taking into account the number of mitotic figures and the diameter of the cell nucleus. It has been found that 18.0% cells were GFAP positive in fields with mitotic figures and in 29.8% cells in fields without mitoses. If the differences in nucleus diameter are concerned the GFAP positive cells constituted 64.2% of cells with diameter between 6 to 10 microns. Instead 78% of GFAP negative cells had a diameter of 6.4 to 7.2 microns. The results indicate that cells with a smaller diameter of the nucleus and localized in fields with mitotic figures are considerably less frequently GFAP positive as compared with cells of larger diameter of the nucleus and localized outside the fields with mitoses. It is suggested that cells of higher differentiation show an undisturbed organization of the cytoskeleton as compared with their counterparts. Thus the determination of GFAP antigenicity can be considered as a tool in the evaluation of differentiation of the tumor and as an indicator of its heterogeneity.