Isolation of prostatic acid phosphatase-binding immunoglobulin G from human sera and its potential for use as a tumor-localizing reagent.

A human immunoglobulin that binds prostatic acid phosphatases (PAP) was isolated from the serum of normal individuals by affinity chromatography using a PAP-Sepharose solid adsorbent. The yield of isolated protein, termed PAP-binding globulin (PAPBG), ranged from 4.7 to 16.3 microgram/ml serum. As shown by immunoelectrophoresis, PAPBG is a gamma-globin of restricted electrophoretic heterogeneity. PAPBG was shown to bind radiolabeled PAP by radioimmune precipitation, and an association constant of 5.0 x 10(4) M-1 was calculated. As determined by immunofluorescence, PAPBG was shown to react with human prostatic tumor cell lines. No binding was detected to other tumor cells examined including those from cultures of human breast, thyroid, pancreas, or normal fibroblasts.