A recombinant fully human monoclonal antibody directed against the human A33 antigen, with potential immunomodulatory and antineoplastic activity. Anti-A33 monoclonal antibody KRN330 recognizes and binds to the human A33 antigen, which may stimulate the immune system to mount a cytotoxic T-lymphocyte (CTL) response against A33-positive colorectal cancers. A33 antigen, a 43 kDa transmembrane glycoprotein of the immunoglobulin superfamily, is highly and homogenously expressed in 95% of colorectal cancer cancers with only restricted expression in normal colonic mucosa and small bowel epithelia.