Arthritis was initiated by injection of K/BxN serum (50 μL per mouse, i.p.; days 0 and 2). On day 8, ilea were harvested from arthritic and naive mice and lipid mediators identified and quantified using lipid mediator profiling (see Methods for details). (A) MS/MS spectrum employed for the identification of RvD5_{n-3 DPA}. Labeled ions are those matching assigned ion fragments for RvD5_{n-3 DPA}. Inset, portion of the molecule that corresponds to each of the diagnostic ions; M, molecular mass. (B) Orthogonal partial least squares discriminant analysis (oPLS-DA) of intestinal lipid mediator profiles. Cumulative tissue concentrations for SPMs (i.e., arachidonic-, eicosapentaenoic acid–, n-3 docosapentaenoic– [DPA–], and docosahexaenoic acid–derived [DHA-derived] proresolving mediators) (C), RvD_{n-3 DPA} (i.e., RvD1_{n-3 DPA}, RvD2_{n-3 DPA}, and RvD5_{n-3 DPA}) (D), and RvD5_{n-3 DPA} (E). Results for A are representative of n = 24 mice; for B are representative of n = 8 mice per group; for C–E are mean ± SEM for n = 8 mice per group from 2 independent experiments; *P ≤ 0.05 versus naive using Mann-Whitney U test. Results are expressed as pg/10 mg tissue.