SYNERGY BETWEEN T-CELL IMMUNITY AND INHIBITION OF PARACRINE STIMULATION CAUSES TUMOR REJECTION

During tumor progression, variants may arise that grow more vigorously . The fate of such variants depends upon the balance between aggressiv eness of the variant and the strength of the host immunity. Although e nhancing host immunity to cancer is a logical objective, eliminating h ost factors necessary for aggressive growth of the variant should also be considered. The present study illustrates this concept in the mode l of a spontaneously occurring, progressively growing variant of an ul traviolet light-induced tumor. The variant produces chemotactic factor s that attract host leukocytes and is stimulated in vitro by defined g rowth factors that can be produced or induced by leukocytes. This stud y also shows that CD8(+) T-cell immunity reduces the rate of tumor gro wth; however, the variant continues to grow and kills the host. Treatm ent with a monoclonal anti-granulocyte antibody that counteracts the i nfiltration of the tumor cell inoculum by non-T-cell leukocytes did no t interfere with the CD8(+) T-cell-mediated immune response but result ed in rejection of the tumor challenge, indicating a synergy between C D8(+) T-cell-mediated immunity and the inhibition of paracrine stimula tion.