Anemia-inducing substance (AIS) in advanced cancer: inhibitory effect of AIS on the function of erythrocytes and immunocompetent cells.

The effects of anemia-inducing substance (AIS), found in the plasma of tumor-bearing subjects, on red blood cells (RBC) and cellular immunity were examined. The results obtained may be summarized as follows: 1) The osmotic resistance and the deformability of RBC were decreased in patients with terminal cancer. 2) Normal human RBC were made less deformable and their membrane was made fragile by treatment with cachectic plasma from those patients, and these changes in physical properties were irreversible. 3) Energy metabolism in RBC was affected by AIS, that is, ATP concentration and pyruvate kinase activity in RBC were lowered and transmembrane glucose influx was suppressed. 4) AIS was removed from cachectic plasma by repeated adsorption with normal RBC, and the inhibitory effect on cellular immunity was lessened as AIS was removed. 5) AIS was detected in cachectic RBC membrane, monocytes, and tumor tissue by indirect immunofluorescence assay using rabbit anti-AIS antibody prepared by us. These observations suggest strongly that tumor-derived AIS appears in the blood of patients with terminal cancer, shows cytotoxicity to RBC and immunologically competent cells, and plays a role in the pathogenesis of cancer cachexy.