Beta2-microglobulin levels of serum and ascites in malignant diseases

Serum beta2-microglobulin levels were measured by radioimmunoassay in patients with various malignant neoplasms, ascitic patients, and also patients with definite or suspected hepatoma showing variable levels of serum alpha-fetoprotein. Elevated serum beta2-microglobulin levels greater than 2.5 mg/liter were found in various malignant neoplasms, especially in multiple myeloma (66.6%) and hepatoma (60.4%) The ascites/serum ratio of beta2-microglobulin levels in the patients with malignant ascites is significantly higher than in those with non-malignant ascites. However, ascites/serum ratios of total protein, IgG, albumin, creatinine levels were not significantly different between the two groups. Levels of serum beta2-microglobulin were correlated well with those of alpha-fetoprotein in the patients with definite or suspected hepatoma (r=0.72, P less than 0.001). From these results it was concluded that (1) high levels of serum beta2-microglobulin in these patients could be attributed to its hyperproduction by tumor cells or by the cells which had been infiltrated and activated, (2) it is useful to estimate the ascites/serum ratio of beta2-microglobulin levels in differentiating malignant from non-malignant ascites, and (3) it might suggest that a function of beta2-microglobulin is in some way related to that of alpha-fetoprotein, and the alpha-fetoprotein-synthesizing cells secrete a great deal of beta2-microglobulin, although its function remains unclear.