Abstract: In the present research, bacterial DNA of pathogenic Escherichia coli was used as co-adjuvant; sheep blood total immunoglobulin G (IgG) was used as the antigen and complete Freund’s adjuvant (CFA) was the adjuvant. Rabbits were injected subcutaneously in the muscle with sheep blood total IgG ± adjuvant in a volume of 2 mL. Forty microgram IgG was suspended in saline with 20 μg soluble bacterial DNA or mixed with CFA with or without bacterial DNA. The study also included two control groups: One group was injected with 1 mL CFA plus 1 mL distilled water, the other group received no injections. Measurement of the proliferative responses by gel diffusion showed that priming with IgG plus bacterial DNA suspended in CFA leads to strong secondary responses to sheep IgG, indicating a strong synergistic interaction between the bacterial DNA and CFA.