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 established1,2. 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 growth5,6; 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 tumour16,17.