Validation of results in a larger cohort of rheumatoid arthritis patients by western blot analysis. To validate results of two-dimensional differential gel electrophoresis analyses, one-dimensional western blots were performed for haptoglobin (Hp)-α1, Hp-α2, apolipoprotein (Apo)A-II and ApoC-III in a larger cohort of rheumatoid arthritis patients (n = 31 responders and n = 19 nonresponders). (A, B) The statistical analysis of the western blot data confirmed the significant upregulation of Hp-α1 and Hp-α2 in responder (R) sera in comparison with nonresponder (NR) sera prior to etanercept treatment initiation (V1) (P = 0.0231, P = 0.0185, respectively) as well as after 6 months of therapy (V6) (P = 0.00445, P = 0.0038, respectively). (C) Interestingly, analysis of Hp phenotypes Hp 2-1, Hp 2-2 and Hp 1-1 revealed that the frequency of the phenotype Hp 2-2 was more common in R in comparison with NR, whereas the phenotype Hp 2-1 was found to be more common in NR. (D) In contrast to proteomics data, the western blot analysis in a larger patient cohort showed an upregulation of ApoC-III in NR sera prior to etanercept treatment (V1) in comparison with responders. (E) During the course of etanercept treatment, no more significant differences between R and NR could be detected. Upregulation of ApoA-II expression was detected in R in comparison with NR only after 3 months (V5) and 6 months (V6) of therapy.