Structural Alterations after in vivo Administration of Phytohaemagglutinin

Abstract

THE addition of phytohaemagglutinin (PHA) to tissue cultures in vitro has been shown to produce the transformation of normal lymphocytes into blast cells which undergo mitosis¹. Although PHA has been widely investigated in vitro, few reports have appeared about the in vivo effects of this plant mitogen. Thus an increase in the mitotic rate of bone marrow cells has been found in young rats after PHA administration². Conflicting results have been reported about the effect of PHA in human anaemias^3–5, the immune response in laboratory animals^6–9 and transplantable tumours^10–11. A marked depression of the carbon phagocytosis has been found after a single large dose of PHA¹². Small doses of PHA, however, do not alter the rate of disappearance of aggregated human albumin from the circulation⁹. Despite the considerable interest existing concerning the in vivo action of PHA, no reports of histological changes have appeared, other than the splenic cellular alteration described by Gamble¹³. This study was therefore undertaken to provide further understanding of the cellular alterations occurring in the spleen as well as in the thymus, lymph nodes and the liver after the in vivo administration of PHA.