DETECTION OF AN INHIBITOR OF CELL-DIVISION IN CULTURES OF TUMOR-CELLS WITH IMMUNOSUPPRESSIVE ACTIVITY INVITRO

  • 1 January 1980
    • journal article
    • research article
    • Vol. 40  (1) , 168-177
Abstract
A number of previous reports described the presence of factors which inhibit the response of lymphoid cells to phytohemagglutinin [PHA]. An inhibitor of cell division synthesized and released directly from cultured [human melanoma MM200 and MM96] tumor cells which appears to have similar immunosuppressive effects in vitro was described. This factor(s) was detected in a wide variety of cultured tumor cells and some cultures of normal fetal tissue. It inhibited the mitogenic response of lymphocytes to PHA and also the spontaneous cell division of a variety of cultured cells including the cells producing the factor. Pulse cytophotometry showed that cells were inhibited in the G1 phase. Production of the factor increased with time and was related to the number of cells in culture. Its synthesis was inhibited by cycloheximide. DNA and RNA synthesis was not required for its production. The factor appeared to have a high degree of biological activity in terms of the number of cultured cells required for production and in regard to the number of cells inhibited. The biological significance of this factor in vivo is unknown but in vitro it inhibited immunoglobulin and mitogen-induced responses which suggests it may play an important role in suppression of the immune response against tumor cells in the host.