The Effects of Antigens and of Phytohemagglutinin on Rabbit Spleen Cell Suspensions by G. Harris,* M.b., and R. J. Littleton

Phytohemagglutinin (PHA) was first shown to be an initiator of mitosis in cultures of normal human leukocytes from peripheral blood (1). Evidence has been presented (2) that the responding cells from human blood had the characteristics of lymphocytes and were derived from a nondividing population. This has been confirmed by other studies (3, 4) which showed that small lymphocytes transformed into a more primitive cell capable of division, and similar results have been described with rabbit peripheral blood cells (5). The present studies were concerned with the effects of PHA on the stimulation of cell proliferation and antibody production by rabbit spleen cells and comparison with the effects of antigens which have been shown to stimulate DNA synthesis in cell suspensions from the spleens of preimmunized rabbits (6). The mechanism of action of PHA is not clear although it has been suggested that it works like an antigen (7) but there is no direct evidence for this except for the fact that the responding cells have the morphological characteristics of cells potentially capable of antibody production. While it has been claimed that human cells, stimulated by PHA, can produce antibodies (8, 9) and that rabbit lymph node explants can produce a specific anarnnestic response to antigens in response to PHA (10) no evidence of immunoglobulin synthesis was found in suspensions of rabbit peripheral blood cells responding to this material (11).