Reactivity of purified GP40 antigen with antibodies from sera of patients with colorectal cancer: A follow‐up study

A glycoprotein antigen (GP40) was previously identified as a major component of immune complexes isolated from sera of patients with Burkitt's lymphoma. Its reactivity with antibodies from sera of patients with various types of cancer was described. In this presentation we describe the methods for further purification of GP40 from Burkitt's lymphoma sera. Radioiodinated purified GP40 was used in a double antibody precipitation assay, to measure the level of free anti‐GP40 antibodies in sera of patients with colorectal cancer. Follow‐up studies of patients at various stages of the disease revealed a close correlation between the level of free anti‐GP40 antibodies and the stage of the disease, namely, low levels in advanced stages (C‐D) and high levels in early stages (A‐B). Furthermore, patients in remission undergoing chemotherapy always had elevated levels of free antibodies. Similarly, patients in relapse had decreasing levels of free antibodies.