THE NEUTROPHIL AS AN INFORMATION TRANSMITTER IN TUMOR-INHIBITION BY ASTREPTOCOCCAL BIOLOGICAL RESPONSE MODIFIER, OK-432

Effective treatment of a rat transplanted ascites tumor by i.p. inject ion of a streptococcal biological response modifier, OK-432, was abrog ated by selective in vivo depletion of neutrophils by a monoclonal ant ibody, RP-3. The mechanisms by which neutrophils participate In the th erapeutic action of OK-432 were studied with Winn's assay using perito neal exudate cells periodically obtained from rats i.p. injected with this biological response modifier. Intraperitoneal resident macrophage s were first activated with OK-432, and within 3 h, tumor-inhibitory a ctivity had moved to the early exuded neutrophils. However, 6 h after injection, exuded macrophages were the only cells involved in tumor in hibition. Considered together with other findings, it is likely that, in this system, neutrophils may transmit information from resident mac rophages to exuded inflammatory macrophages in a series of responses i nduced by i.p. injection of OK-432.