For DN2 B cells, pSYK, pPI3K, and pERK1/2 stimulation indices were positively associated with the erythrocyte sedimentation rate (ESR; ρ = 0.34, 0.39, 0.60, respectively), as depicted in Fig. 6A. When r-axSpA patients were categorized (yes/no) based on having a history of ESM, Ankylosing Spondylitis Disease Activity Score (ASDAS) ≤2.1, or CRP levels ≤5 mg/L we did not observe differences in BCR signaling responses (data not shown). Here, CRP is linked to ankylosing spondylitis.