Contribution of myeloid and lymphoid host cells to the curative outcome ofmouse sarcoma treatment by photodynamic therapy

Selective depletion or inactivation of specific myeloid populations (neutro phils, macrophages) and lymphoid populations (helper T cells, cytolytic T c ells) in EMT6 sarcoma-bearing mice was used to determine the contribution o f each of these host immune cell types to the curative outcome of Photofrin -based photodynamic therapy (PDT). Immunodepletion of neutrophils and cytol ytic T cells initiated immediately after PDT resulted in a marked reduction in PDT-mediated tumor cures. Significant reduction in the cures of EMT6 tu mors was also achieved by immunodepletion of helper T cells and inactivatio n of macrophages by silica treatment. The initial tumor ablation by PDT was not affected by any of the above depletion treatments. These results provi de direct evidence that the contribution of neutrophils, macrophages and T lymphocytes is essential for the maintenance of long-term control of PDT-tr eated tumors. (C) 1999 Published by Elsevier Science Ltd. All rights reserv ed.