As far as a physiological state of immune system cells is of great importance, for the investigation of the growth hormone influence on spleen T-lymphocytes ability to divide, we utilised plasmid-mediated gene transfer of hGH cDNA regulated by a powerful human cytomegalovirus immediate-early (CMV-IE) enhancer-promoter. The femur muscles of mice were injected with 50 mg of the plasmid DNA and then electrostimulated. 7 days later muscle tissues were harvested, and hGH DNA and RNA presence were proved by Southern and Northern blot analysis, respectively. Splenocytic proliferative response after ConA stimulation was shown to be increased by 6.8 times in experimental mice comparing to controls. Besides that in mice treated with plasmid vector increased cellularity of spleen. These results demonstrate that gene transfer of hGH is one of possible methods to increase immunity in aging organisms.