Immunosuppressive Acidic Protein (IAP) in the serum of 58 patients with malignant tumor and 13 normal individuals was quantitatively determined by single radial immunodiffusion. The IAP values in 46 epidermoid carcinomas and 12 malignant lymphomas ranged from 697.4+350.8μg/ml to 829.0+372.0μg/ml, significantly higher than those of normal individuals (389.2+93.1μg/ml). The upper limit of normal is usually considered to be 500μg/ml. The IAP value rises as the clinical stage of the tumor advances.
Actually, the highest value of IAP in stage IV patients was 888.2μg/ml, and 81.8% of the patients had IAP values above 500μg/ml. An additional experiment showed that natural killer activity of lymphocytes from the patients with malignant tumors correlated well the IAP levels.
It is concluded that IAP values not only reflect the immune state of tumor patients, but also are very useful in clinical diagnosis.
