The objective of the investigation was to study the influence of RNA isolated from the brains of immunized mice on the immune response in syngeneic recipients. (CBAxC57BL/6)F1 male mice immunized by SRBC and RRBC were used for isolation of experimental RNA. Mice injected with medium 199 were used for isolation of control RNA. Experimental and control RNA was injected into syngeneic mice recipients immunized by SRBC, RRBC or rat RBC preliminary. It was shown that experimental RNA stimulate the specific immune response only.