Small DNA Fragments Trigger Antibody Response in Rabbits, 1965 Study Finds

Plesca and colleagues, reporting in Science in 1965, investigated whether small fragments of DNA could act as haptens to provoke an immune response. In the study, calf-thymus DNA was broken down into small pieces called oligodeoxyribonucleotides, roughly the size of four-to-six-unit nucleotide chains (tetra- to hexanucleotides). These fragments were chemically linked to methylated bovine serum albumin, emulsified in complete Freund's adjuvant, and injected into rabbits — a classic animal-model approach for raising antibodies against a target molecule.

The researchers found that serum from the immunized rabbits contained antibodies that reacted with both homologous (rabbit-derived) and heterologous (from other species) unfragmented, heat-denatured DNA. These antibodies also reacted with a synthetic polydeoxyribonucleotide — specifically a polydeoxyadenylate-thymidylate polymer, a lab-made DNA-like molecule built from repeating adenine and thymine units.

The key finding is that even very small DNA fragments can serve as effective haptens, meaning they can drive the production of antibodies against DNA structures despite their small size. The authors note this raises the possibility of eventually generating antibodies specific to unique nucleotide sequences.

This is a mid-20th-century immunology and biochemistry study conducted in rabbits, using calf-thymus DNA and a synthetic polynucleotide as laboratory reagents. It says nothing about skin biology, tissue repair, or any therapeutic application — the "polydeoxyribonucleotide" here is a synthetic experimental polymer used to test antibody cross-reactivity, not a biological or medicinal agent, and the abstract does not describe any wound-healing, dermatological, or clinical outcome.