The review article is devoted to a role of pluripotent stem cells and immune system in renewal of tissues (regeneration). Cell-precursors (progenitor cells) and differentiated cells can be divided a limited number of times and aren't capable of ensuring regeneration of tissues during the whole process of ontogenesis. The renewal of tissues during the whole long period is impossible without the participation of a specialized system which is responsible for regeneration. The given system is made up of pluripotent stem cells which are capable of differentiating themselves into all types of somatic cells, and into a line of genital cells. These stem cells are also capable of reproducing themselves over the whole lifespan of the organism. The participation of pluripotent stem cells and the possible mediation of antigen-presenting cells and T-helpers/T-suppressors in the complex with molecules of the MHC I class/II class make it possible to consider that exactly this immune system is responsible for regeneration of tissues in the organism. The participation in the regeneration process is the most important (and perhaps the leading) function of the immune system. With age the quantity of pluripotent stem cells gradually decreases. It leads to violation of renewal of tissues at people over 35-40 years old. Transfusion of mononuclear fraction of peripheral blood procured from young donors 18-23 years old with the same blood groups and sex as the recipient (RF patent number 2350340), allows people over 40-50 years old to reestablish the pool of pluripotent stem cells and the process of tissue renewal.