Alive and non-pathogenic microorganisms, including the strains of lactic acid bacterium, such as: Bifidobacterium, Lactobacillus, Enterococcus, Propionibacterium, Lactococcus, Saccharomyces, Bifidus or Streptococcus salivarius and yeast of Saccharomyces boulardii, have a favorable salubrious effect in a host via stimulation of the Th1 response and the decreased immune response of Th2. Probiotic bacteria influence apoptosis of the gastrointestinal tract affecting the cells of intestinal mucosa epithelium and of the immune system, e.g., T lymphocytes, as well as modulation of the production of numerous proinflammatory and proapototic cytokines. Cytokines produced by auxiliary lympocytes of the Th1 profile, such as: IL-1, IL-6, IL-8, IL-12, IL-18, TNF-, and INF- are associated with the I type of an immune response and they intensify apoptosis. Prebiotics strengthen the proapoptotic qualities of probiotic bacteria. During metabolism short-chained fatty acids are formed in the large intestine, stimulating the growth of probiotic bacteria of Lactobacillus and Bifidobacterium. Inducing apoptosis in the gastrointestinal tract by probiotic bacteria and probiotics intensifying their activity prevents further progression of inflammatory changes in the mucosa towards neoplastic changes. Synbiotics seem to be the future of medicine, but their influence on apoptosis in the gastrointestinal tract requires further research.