To examine if antibody responses differ according to disease stage, we studied a cohort of 21 patients diagnosed with stage I, II, III and IV melanoma (Table 1 ) and evaluated the reactivity of antibody cultures (n = 1,800) from these patients to the metastatic melanoma cell line A-375 utilizing the cell-based ELISA. This patient cohort was almost exclusively Caucasian. Antibody reactivity against melanoma cells was quantified relative to a non-specific human IgG control and measured as fold increase above this negative control. Patients with local (non-metastatic, stages I and II) disease had a significantly (P,0.0001) higher mean antibody response (2.6 fold increase, 95% CI = 2.4 to 2.8) compared to those with confirmed metastatic disease (stages III and IV, 1.7 fold increase, 95% CI = 1.7 to 1.8) (Figure 3 , A). We also found an overall significant reduction (P,0.0001) in the mean reactivity of antibodies secreted in B cell cultures against melanoma cells from stage II (2.8 fold increase, 95% CI = 2.6 to 3.0, n = 660) to stage III (1.9 fold increase, 95% CI = 1.8 to 2.0, n = 540) and to stage IV patients (1.5 fold increase, 95% CI 1.5 to 1.6, n = 480) (Figure 3 , B). The stage I patient was not evaluated since samples from only one patient (n = 120 B cell cultures) from the cohort was available to include in this group. The highest mean antibody reactivity against melanoma cells was observed in Patients 5 and 6 diagnosed with stage II and III melanoma, respectively (Table 1 ). However, we observed variation in the antibody response among individual patients, with 19 out of 21 patients in our cohort having at least one antibody-producing culture with optical density values 2.5-fold above the negative IgG control (Table 1 ). These findings suggest that despite the significant reduction in the proportion of tumor-reactive antibody cultures as a function of disease progression, patients from each of stage groups had B cells with antibodies that recognized tumor cells.