Immunosuppression is one of the most common reasons for the failure of immune-system to control tumor progression. Circulating immune-complexes (CICs) are one of the major contributing factors to induce as well as to maintain immune-suppression in tumor bearing host. Removal of CICs can reduce the burden of immunosuppressive factors, which helps to achieve immunopotentiation and anti-tumor effect. Protein A (PA) of Staphylococcus aureus Cowan I (SAC), is well known to bind with CICs more efficiently compared to immunoglobulins. Therefore, PA of SAC is used to remove CICs from ascites fluid (cell free). Adsorbed ascites fluid (ad-ASF) was used to treat ascites tumor bearing animals. This therapeutic intervention showed to have potential for the treatment of ascites tumor bearers, at least at experimental levels. This treatment has shown potentiation of both humoral immune response as well as cell mediated immune response. This book will be useful for post-graduate and doctoral students of life-sciences as well as researchers actively engaged in anti-tumor and immune-modulatory properties of biological response modifiers.