Experimental studies using monoclonal antibody have demonstrated that anti-idiotypic immunity can be enhanced by microspheres or cytokines. The underlying physiological principles behind these strategies involve sustained release of antigen and arousal of the immune system. In this study, a murine model was used to investigate the combination effect of microspheres and cytokines on anti-idiotypic response. A single chain antibody scFv-pDL1.0, which recognizes the human ovarian cancer antigen CA125 was formulated in microspheres and injected to mice alone or in the presence of colony stimulating factor (GM-CSF) or tumor necrosis factor (TNF-). The immunization of mice with formulated single chain antibody and cytokines resulted in enhanced production of anti-idiotypic antibody, and which subsequently induced the production of anti-anti-idiotypic antibody. These results raise the possibility of cancer immunotherapy by administration of single chain antibody encapsulated in microspheres with GM-CSF or TNF-.