Resistance to tumor graft in mice treated with inactivated Brucella abortus cultured in smooth or rough phase.

Because killed Brucella abortus organisms cultured in smooth (S) or rough (R) phase were known to differentially influence humoral and cellular immune responses and to differ in their effects on T-dependent responses, the antitumor properties of killed B. abortus organisms, cultured in S- or R-phase and then inactivated, were compared in (C57BL/6 X DBA/2)F1 female mice with the use of 6 different transplantable tumors. In solid tumors, the antitumor effects produced by S-preparations were never improved by R-preparations. However, in ascites tumors, R-preparations gave the best antitumor results. These findings suggested that the defense mechanisms acrivated by immunostimulants may differ according to the site of tumor implantation. Among the other experimental factors studied, the route of B. abortus administration had a prominent role. Local injection at the site of tumor implantation before or after the graft gave better results than did systemic treatment. Systemic treatment could enhance the growth of Lewis tumor when applied 5 or 10 days before tumor graft but generally had an antitumor effect when given 1 day after the graft.