[Serum factors that inhibit in vitro immunological reactions in malignant tumor development in experimental animals].

In two immunological reactions (immunocytoadherence and inhibition of macrophage adherence in the presence of specific antigens) it was shown that autologous and homologous native sera in some percentage of cases render an inhibitory effect. One of the blocking factors of sera proved to be rather thermostable, the other, on the contrary, to be thermolable.