B cell chemoattractant CXCL13 was decreased after treatment with pateclizumab. Mean ± SEM levels of CXCL13, a B cell chemoattractant, are presented over time after treatment with adalimumab, pateclizumab, or placebo. CXCL13 was decreased following treatment with pateclizumab, demonstrating pharmacological engagement of the LTα pathway, as observed in the phase 1 trial of pateclizumab . Adalimumab also modulated CXCL13 levels to a similar degree. Significance was assessed at the efficacy endpoint (Day 85); see Methods. *P <0.05 vs. placebo. LTα, lymphotoxin alpha; SEM, standard error of the mean.