Immune reactivity in vitro to spontaneous canine oral tumors

In vitro reactivity of autochthonous lymphocytes to tumor cells from progressively growing oral tumors in dogs was studied. Tumors were collected during surgery or before necropsy and prepared for tissue culture. Only viable, glass-adherent tumor cells were used. The cells were first incubated either with culture medium or with canine serum, and then they were mixed with lymphocytes. The cultured tumor cells were destroyed by high numbers of lymphocytes, but the reactivity was blocked for tumor cells that had been incubated with autologous serum. Tumor cell growth was stimulated by low numbers of lymphocytes. These results point out the complexity of tumor enhancement in vivo.