A monoclonal antibody which discriminates between sub-types of astrocytoma

A monoclonal antibody, M2, was produced by somatic cell hybridisation of splenocytes, from mice immunised with human fetal brain, with the murine myeloma cell line NS-1. Indirect immuno-peroxidase staining of formalin-fixed, paraffin embedded tissue sections showed that, whilst the monoclonal antibody gave a positive reaction with 32/39 astrocytomas from adult patients and 33/36 of children's astrocytomas of the adult histological type, only 17/39 of juvenile astrocytomas were stained. A Chi-squared test showed that the difference in staining between the two groups (adult versus juvenile) was highly significant (p less than 0.0001). In contrast, using a polyclonal antiserum to GFAP, a significantly larger proportion of juvenile astrocytomas than adult astrocytomas stained positively (p less than 0.05). Thus, whereas the distribution of GFAP accorded with the general finding that the degree of malignancy of a tumour correlates with the loss of cell type specific markers, the distribution of M2 reactivity was similar to that of some oncogene products which increase with malignancy. From the flow cytometry data it is apparent that the antigen recognised by M2 is not cell cycle dependent.