MAD-CT-5-specific IgG antibodies can be detected by ELISA. (A) IgG antibodies specific for the SSB antigen (MAD-CT-5) were analyzed by ELISA (Kallestad Anti-La Test Kit, Bio-Rad). The colorimetric ELISA is shown. A1, B1: Negative controls. C1, D2: 0 U/mL. E1, F1: 2 U/mL. G1, H1: 8 U/mL. A2, B2: 30 U/mL. C2, D2: 100 U/mL standards. E2, F2: Positive control sera. A3-H4: Sera from subjects without MAD-CT-5 immunoreactivity. A5, B5: Sera from subject # 20, from which MAD-CT-5 was originally identified. (B) ELISA was conducted with sera obtained from 47 male control blood donors, 37 subjects with early-stage (nonmetastatic) prostate cancer, and 58 subjects with metastatic prostate cancer. The SSB-specific IgG in U/mL is shown, determined by comparison with a standardized control. The line represents the mean +3 SD of data from the normal control population, above which results were classified as positive.