Morphologic alteration of small lymphocytes in culture into large blast-like cells able to synthesize DNA and RNA and to divide mitotically. It is induced by INTERLEUKINS; MITOGENS such as PHYTOHEMAGGLUTININS, and by specific antigens. It may also occur in vivo, as in GRAFT REJECTION and chronic myelogenous leukemia (LEUKEMIA, MYELOID, CHRONIC).
