Fraction of sera positive at different antibody levels. In A, the percentage of B-Raf positive sera of control patients (△) or melanoma patients (■) is plotted as a function of the cut off titer, whereas sera are termed positive if the titer reaches or exacerbates the given cut off titer. The difference between control patients and melanoma patients was statistically significant for a cut off titer of 1:300 (P = 0.028; 0.073; 1.0, two sided Fisher's exact test for cut off titers equal to 1:300; 1:900 and 1:2700 respectively). In B, the percentage of sera with titers higher or equal than 1:300 is shown for B-Raf V599E, B-Raf and C-Raf specific responses. In all cases, the amount of antibody positive melanoma patients is higher compared to the control group. This trend was significant for the comparison of B-Raf positive sera (P = 0.028, Fisher's exact test) and not significant for the comparison of B-Raf V599E (P = 0.12, Fisher's exact test). However, C-Raf specific antibodies with titers of 1:300 were only detectable in 1.8% of the tested sera from melanoma patients and none of the control patients (P = 0.327).