Enhancement of antibody response to soluble HSA antigen of young rabbits pretreated with deoxyribonucleic acids from adult donors.

Rabbits were injected with one dose of 2-4 mg. isolated nuclear DNA (from spleens of adult donors) at 3-5 days of age and their antibody response to a later administered soluble HSA antigen was followed. A) Rabbits receiving antigen only at 9 days of age, without previous DNA, did not form antibodies even after the second dose of HSA antigen given at 8 weeks of age. Nor were antibodies detected in the serum of rabbits treated before antigen, i.e., at 4-5 days of age, with DNA-N (from spleens of non-immunized rabbits), or DNA-P (from spleens of the pig immunized with a different antigen). Only rabbits treated with DNA-Ia (from spleens of rabbits immunized with soluble HSA antigen) formed antibodies to HSA antigen given at 9 days after birth. Antibodies were detectable in the serum at 21 days after antigen administration and retained increased levels as long as 50 days after the first dose of antigen. B) When HSA antigen was injected at 17-18 days after birth, even the DNA-N (4 mg.) given at 3-5 days after birth increased the antibody response in the recipients. Substantial acceleration and increase in antibody formation was obtained in rabbits treated with DNA-Ib after birth as compared to control rabbits (after antigen only with DNA). On the contrary, DNA-H from spleens of rabbits intensively immunized with HSA in adjuvant, given in a larger dose (4 mg.), suppressed the antibody response of rabbits over 8 weeks of age after the second dose of antigen. DNAs from spleens of immunized donors injected into rabbit offspring, without subsequent HSA antigen administration, did not lead to the appearance of detectable anti-HSA antibodies in the serum of young rabbits under the conditions of our experiments A and B. Long-term effects of DNAs injected in the postnatal period into rabbits on their immune response are discussed.