MITOGENIC properties of extracts from Phytolacca americana (pokeweed, scoke, inkberry) for human peripheral blood cells in vitro have been reported from this laboratory. Subsequently, the appearance of leukocytes typical of early and late members of the plasmacytic series was described in the peripheral bloods of two of the authors (P.F. and B.E.B.), who received accidental systemic exposure to the mitogen. Effects of phytomitogens on human cells in vivo are not established, although a number of investigators have administered phytohemagglutinin from Phaseolus vulgaris to patients with aplastic anemia, hoping that the "transformed" lymphocytes might possess hematopoietic potentialities and repopulate the marrow with useful cells. Interpretations of such studies have been complicated by the small numbers of patients studied, the natural course of this group of anemias, simultaneous use of other therapy, and other variables.
More information has been accumulated about the effects of phytomitogens on peripheral blood cells in vitro. The process of "transformation" or blastogenesis of lymphocytes, whether induced by plant extracts or specific antigenic stimuli, appears to involve an immune mechanism, although morphologic differentiation toward the plasmacytic series is not seen in the in vitro environment.
Recently, we have had the opportunity to study serial blood films from children who received systemic exposure to pokeberry, either through proven oral ingestion (berries recovered from vomitus), or by exposure of fresh cuts and abrasions to pokeberry juice in the course of handling the berries. In each of these instances large cells morphologically typical of plasmablasts and proplasmacytes, and mature plasma cells were found in the peripheral blood films for periods up to 2 weeks following exposure. Mitotic cells were present in the peripheral blood during the first 10 days after exposure (Fig. 1 and 2).
Natural killing of tumor cells by human peripheral blood cells. Suppression of killing in vitro by tumor-promoting phorbol diesters.