Hybridoma process: ultrastructural cytology of different stages.

In order to define the ultrastructure of the hybridoma cell and to learn more about the plasmocytic differentiation process, a scanning (SEM) and transmission (TEM) electron microscopy study of several cell types involved in the production of monoclonal antibodies was performed. Cells of the three different stages in hybridoma process were studied. These cells included NS/1 murine myeloma cells, 40-3A4 in vitro cultured hybridoma and 33-1D2 ascitic tumor hybridoma cells. A stereological analysis of the Sv parameter (surface of RER per volume unit of cytoplasm) was performed in the murine myeloma line, the in vitro cultured hybridoma and the ascitic tumor hybridoma. In order to comparatively evaluate the plasmocytic differentiation of these cells the same methodology was applied to splenic lymphocytes from immunized mouse and to mature human myelomatous plasma cells. As expected, during the hybridoma process, a progressive increase in the amount of RER was detected. This was in contrast with the surface characteristics of the cells which become progressively smooth when the hybridoma was cloned, either in vitro or in vivo. From these results it can be inferred that the amount of RER is a more reliable parameter than surface blebs as a morphological element indicative of plasmocytic differentiation. On the other hand, numerous viral particles were present not only in murine myeloma line but also in hybridoma clones secreting monoclonal antibodies.