Pregnant Wistar female rats were injected with polyclonal rabbit antibodies (AB) to S-100 brain protein. Control groups received equivalent amount of AB to bovine serum albumin or non-immune rabbit's IgG. An increased level of anti-S100 immunoreactivity was detected by ELISA or its enhanced variant ASPAG (from Amplified Solid Phase Attached Antigen-Antibody Grid formation) in the serum of 1 month old offsprings of group treated with AB to S-100. Obtained data indicate the possibility of inborn epigenetical "imprinting" of specific autoimmune reactions which may be important for the development of certain forms of nervous system diseases.