Bovine monocyte-induced tumor cell cytotoxicosis

Human monocytes have been shown to be highly cytotoxic for tumor cells in vitro. Th determine whether these observations could be extended to the bovine species, monocyte-induced tumor cell cytotoxicosis was examined in vitro. Target cells were initiated from benign hyperplastic corneal plaque lesions or ocular squamous cell carcinoma lesions in cattle. The monocyte-induced tumor cell cytotoxicosis, as measured by target cell [3H] thymidine incorporation, was highly significant (P less than 0.001) in corneal plaque cells at target: effector cell ratios of 1:10, 1:5, and 1:1. The [3H] thymidine incorporation was also highly significant (P less than 0.001) in squamous cell carcinoma cells at target:effector cell ratios of 1:10 and 1:5, but of less significance (P less than 0.01) at 1:1. Further, the ability of bovine monocytes to kill target cells was enhanced by culturing effector cells for 3 days before assay. These data show that bovine monocytes are cytotoxic for tumor cells in vitro and indicated that bovine monocytes may be of importance in the control of neoplastic proliferation in vivo.