Stereological study of murine myeloma and hybridoma cells in vitro and in vivo.

Stereologic ultrastructural methods were applied to several cell types involved in the production of monoclonal antibodies against the mitochondrial enzyme glutamic dehydrogenase (GDH). These cell types included SP2/O murine cells, in vitro cultured hybrid cells producing monoclonal antibodies, and the same hybrid cells maintained as solid and ascites tumors (TH and ATH cells, respectively). The statistical analysis of quantitative data indicates that the fusion between SP2/O cells and spleen lymphocytes does not induce significant changes in the fine structure of the former cells. Moreover, the transfer of hybrid cells from in vitro to in vivo conditions induces their transformation from an immature state to mature plasma cells. The increase in mitochondria and rough endoplasmic reticulum suggests that the ascites tumor provides cells with an environment more suitable for expressing their activity than does the solid tumor.