EFFECT OF MYELOPID ON THE T-SYSTEM OF IMMUNITY AND DEVELOPMENT OF TRANSPLANTABLE B16 MELANOMA IN C57BL/6 MICE

Three stages of tumorigenesis/latent, settling and progression/were generated after C57BL/6 mice were grafted 2.10(4) or 1.10(6) B16 melanoma cells. 250 mug and 300 mug of myelopid given s. c. at a dose 50 g daily, delayed the tumour growth depending on the inoculum size. Long-term inhibition was observed at small dose of tumour cells transplanted, but a transitory effect was obtained at the large dose. T-cell activity in the thymus and regional draining lymph nodes was evaluated by morphometrical criteria. Generation of thymic and lymph node T-cells was enhanced at early stages of the tumour growth. Myelopid treatment did not change this activation but resulted in a decrease of the amount of the lost cells. The progression stage was characterized by the fast delevopment of T-immunodeficiency following the short-term activation of T-cells generation. Myelopid injections caused strong but short-term central generation of thymocytes without prevention of subsequent T-deficiency.