The present invention relates to methods of using neutral soluble glucan and monoclonal antibodies for antitumor therapy. Neutral soluble Beta (1,3 1,6) glucan (NSG) enhances the tumoricidal activity of the innate immune system by binding to the C3 complement protein receptor CR3. The glucan does not stimulate the induction of inflammatory cytokines. Also described are methods of using whole glucan particles (WGP) as an immunomodulator by inducing a shift from a Th2 response to the Th1 response, leading to an enhanced antitumor cytotoxic T-cell response.