Lymphoma-associated antigen (LAA): Isolation, characterization and clinical evaluation

Abstract

Lymphoma-associated antigen (LAA) was isolated from lymph nodes of confirmed Hodgkin's and non-Hodgkin's lymphomas by saline extraction, centrifugation and ammonium sulphate fractionation and then purified by G-200 Sephadex chromatography which revealed its mol.wt at 29 K daltons. By sucrose density-gradient centrifugation the mol.wt of LAA was 43 K daltons. Physicochemical properties of LAA were determined. In polyacrylamide gel LAA separated as a discrete protein with electrophoretic mobility of alpha-globulin at pH 8.6. The pI was 5.04 and sedimentation coefficient between 3S-4S. Xenogeneic antiserum was raised in rabbits and purified by cross adsorption and affinity chromatography. By immunochemical methods, LAA was detected in the sera and body fluids of most lymphoma patients and was absent from normal individuals and patients with other types of cancer. A radioimmunoassay procedure was developed and preliminary studies revealed that the lymphoma sera at 1:5 and 1:10 dilution inhibited the binding of labelled LAA by antibody, whereas the sera of normals and controls exhibited no such inhibition. The sensitivity of this assay was 22 ng ml-1. The serum LAA levels were in the range of 187-1500 ng ml-1. These results were also confirmed by the indirect inhibition assay using conjugated peroxidase. Serial determination of serum LAA by RIA indicated a positive correlation with the course of disease.