In Vitro Immune Stimulation-Inhibition to Spontaneous Canine Tumors of Various Histologic Types

Abstract

Utilizing dogs with progressively growing tumors we are reporting on the in vitro reactivity of their lymph node or peripheral blood lymphocytes to their own tumor cells. Tumors, lymph nodes, and blood were collected aseptically during surgical treatment or before necropsy. Primary cultures were set up and shortly thereafter only viable glass-adhering tumor cells were utilized. The cells were first incubated with either media or various sera and then varying numbers of sensitized lymphocytes were added. The mixtures were incubated for 90 min in rotating test tubes and then plated into culture dishes or plates. Two and/or 5 days later, the cultures were fixed, stained, and viable target cells were counted. In vitro tumor cell destruction by high numbers of lymphocytes from dogs bearing tumors and the blocking of such reactivity by autologous serum were demonstrated. Serum from dogs with the same histologic type of neoplasm inhibited allogenic lymphocyte cytotoxicity, whereas serum from dogs with a different tumor, normal dogs, and a dog who had been clinically free of osteosarcoma after limb amputation 17 months earlier, did not significantly block the cellular-mediated reactivity. Stimulation of tumor growth in vitro by low ratios of sensitized lymphocytes to tumor cells was demonstrable. Autologous serum from dogs with progressively growing neoplasms appeared to potentiate the stimulation of tumor growth above a simple blocking of lymphocytic-mediated cytotoxicity. These results confirm our earlier reports of immune stimulation to tumor growth in vitro and support the hypothesis and work by Prehn that the early immune response to neoplasia might directly stimulate rather than inhibit tumor growth.