The review summarizes experimental and clinical data about the influence of Lactobacillus on the immune system. A conclusion is made that the effect of Lactobacillus is a multifactor process. After entering the intestinal tract live microorganisms or biologically active substances produced by them may activate specific and nonspecific systems of microorganism protection. Experimental and clinical data about the action of Lactobacillus as adjuvants to the humoral immune response are presented. The mechanisms of anticancerogenic action of Lactobacillus and their cell wall components are analyzed in detail. The prospects for the use of Lactobacillus as probiotics in medicine are considered. The conclusion about positive value of the multifactor action of these microorganisms on the human immune system is made, since no negative effects are evoked by the discussed mechanisms of specific effect of Lactobacillus. This opens wide possibilities for the development of application schemes of probiotics from lactobacillus for the stimulation of several functions of the immune system, creation a new forms of antitumor drugs and combination of them with oral vaccines for improving their immunogenicity.