Collagen type II-induced arthritis (CIA) is a disease, which includes inflammatory and autoimmune reactions. Spleen protein extracts were subjected to 2D-DiGE and MS-MALDI-TOF/TOF analysis to identify proteins that were different in concentration ally expressed in CD38-KO and B6 WT mice with arthritis or with inflammation. Using multivariate analyses, in Col-II-immunized mice 20 differentially expressed spleen protein species were able to discriminate between WT and CD38-KO mice. Among them, multiple serotransferrin (Tf) species were identified. In contrast, in CFA/IFA-treated mice, the distinct protein profile, which discriminates between CD38-KO and WT mice, was unrelated with Tf. Unexpectedly, non-immunized CD38-KO mice showed a distinct proteome profile as compared with that in non-immunized WT mice, and again multiple protein species were identified as Tf. By using a LC-TOF-MS method to separate and detect Tf glycopeptide glycoforms in serum samples, differences in the Tf glycosylation pattern between CD38-KO and WT mice sera were found in both non-immunized and CIA+ mice. Data on Tf spots separated by 2-DE indicate differences in glycosylation related with NeuGc content. In summary, Tf changed significantly in its glycosylation pattern in mice with arthritis