Cytotoxic Effects of Peritoneal Neutrophils on a Syngeneic Rat Tumour

Abstract

SPECIFIC immunological phenomena directed against tumour cells which influence their behaviour and growth in vivo and in vitro have been clearly established^1,2. In contrast, nonspecific defences against cancer have received little attention, although such mechanisms are important in preventing microbial infection³. Recently there have been indications that such non-specific defences against cancer cells exist but the underlying processes are undefined. Increases in reticuloendothelial activity frequently occur during tumour growth⁴; stimulants of non-specific defences, such as the BCG strain of Mycobacterium tuberculosis and Corynebacterium parvum, inhibit tumour growth^5,6; and induction of inflammation by vaccinia⁷ or dichloronitrobenzene⁸ in skin overlying a tumour may induce regression. Most attempts to analyse these phenomena implicate unsensitized lymphocytes⁹ and macrophages¹⁰, although the cytotoxic properties of these cells compared with specifically sensitized cells are low¹¹. Little has been written about the possible role of neutrophils, although their presence in tumours is not infrequent¹². The probable role of neutrophils in contributing to the cytotoxic activity in vitro of leucocyte populations towards various allogeneic and syngeneic cell types has been discussed¹³ and Bubenik et al.¹⁴ have postulated an action of neutrophils against human bladder tumours. Recently Godleski et al.¹⁵ showed movement of neutrophils towards cells of Walker carcinosarcoma 256 growing on chick chlorioallantoic membranes or cover-slips, followed by contact and damage to tumour cell membranes. This article describes preliminary studies demonstrating in vitro and in vivo a significant cytotoxic effect of rat peritoneal neutrophils against a syngeneic ascites tumour, WBP1(A), < 10 cells of which will produce a tumour^16,17.