The presence of retroviral particles in hybridoma cell lines.

The presence of very high numbers of type C and type A retroviral particles was repeatedly confirmed not only in myeloma cells NSI, Ag 8 and in thymoma cells BW5147, EL 4 but also in B and T cell hybridomas constructed from the myeloma and thymoma cells used. Retroviral particles were demonstrated by current electron-microscopic and physicochemical methods. Biological tests for the induction of possible malignant or any pathological changes in the artificially infected sensitive cells during long-term cultivations in vitro or in vivo gave negative results. Nevertheless, on account of the hitherto unknown action of retroviruses one can suppose that monoclonal products from B and T cell hybridomas, particularly when used for practical purposes, should be purified because of their infectious nature.