Enhancement versus tumor resistance induced by different levels of immunodepression in BALB/c mice with protozoan infections.

The relationship between the growth pattern of a spontaneous syngeneic adenocarcinoma and the immunodepression state caused by Trichomonas vaginalis and Trypanosoma congolense infection was evaluated in syngeneic BALB/c mice. We show that in T. vaginalis infected mice a slight and transient depression of both humoral and cellular immune reactivity induces an enhanced tumor growth. By contrast, a marked and long lasting depression of both humoral and cellular immune reactivity in mice infected with T. congolense occurs together with a delay in tumor take and a slower tumor growth. The various parameters affecting tumor growth in protozoan infected mice are discussed.