Annotation: The study of the mechanisms of spontaneous regression of malignant tumors is a topical issue of our century. Disclosure of the pathogenesis of regression will allow progress in the treatment of such diseases. The article discusses the mechanisms of regression of malignant tumors in inflammation, discloses the role of bacteria in this issue, and analyzes the possible mechanism of immunity sensitization in such diseases. The review of immune mechanisms was carried out on the basis of these articles, which studied the Coli toxin, BCG vaccine. The results showed the effectiveness of the use of these funds in the treatment of cancer patients. The possibilities of using bacteria for the transfer of drugs to the tumor area and their production of cytokines are also described. In addition, the correlation between the time of onset of inflammation and regression of tumor formation was analyzed. The main antitumor compounds and substances (IL-1, IL-12, TNF family, LIGHT and CCL21) were also noted, their effect on tumor cells and their role in the regression of malignant tumors was described. As a result, it was concluded that bacteria increase the ability of the immune system to recognize and attack tumor cells, however, the individual characteristics of the reactivity of the human immune system should be taken into account before such therapy.